Dietary Carbohydrates, Meal Composition, and Postprandial Glycemia in Type 2 Diabetes: A Narrative Review With Implications for CGM-Guided Personalized Nutrition

By Ori Scott, M.Sc. NutritionRegistered Dietitian (Israel)Founder, Healthy Habits Coaching

Abstract

Background

Medical nutrition therapy is an integral component of type 2 diabetes (T2D) management. Nevertheless, questions concerning carbohydrate intake remain among the most difficult to translate from population-level evidence into practical dietary recommendations. Patients frequently seek categorical guidance regarding carbohydrate restriction, fruit, grains, glycemic index (GI), meal composition, nutrient sequence, meal timing, and postprandial glucose excursions. Contemporary professional recommendations instead emphasize individualized dietary patterns and carbohydrate quality rather than a universal carbohydrate prescription.

Objective

This narrative review examines recent evidence concerning carbohydrate quantity and quality, dietary fiber, whole grains and fruit, GI and glycemic load (GL), mixed-meal composition, nutrient sequence, meal timing, dietary patterns, and continuous glucose monitoring (CGM) in adults with T2D. Particular attention is given to the distinction between the intrinsic characteristics of individual carbohydrate-containing foods and the glycemic response produced when those foods are consumed as components of mixed meals.

Methods

A focused narrative review of literature published from 2021 through September 2026 was undertaken. PubMed/MEDLINE-indexed human studies and contemporary clinical recommendations from the American Diabetes Association (ADA), the European Association for the Study of Diabetes (EASD) and its Diabetes and Nutrition Study Group (DNSG), and the American Association of Clinical Endocrinology (AACE) were prioritized. Systematic reviews, meta-analyses, randomized controlled trials (RCTs), and evidence-based professional recommendations relevant to adults with T2D were preferentially included. Animal and in vitro studies were excluded from the clinical synthesis.

Results

Current evidence does not establish a single optimal carbohydrate intake for all adults with T2D. Lower-carbohydrate dietary approaches may improve glycemic outcomes, particularly over shorter periods, but their comparative advantage tends to diminish with longer follow-up. Carbohydrate quality remains clinically important irrespective of total carbohydrate intake. Dietary patterns emphasizing minimally processed, fiber-rich foods—including vegetables, legumes, whole fruits, and whole grains—are consistently supported by contemporary U.S. and European recommendations.

Lower-GI/GL dietary patterns can produce modest improvements in glycemic control. However, the GI of an individual food should not be interpreted as a sufficient predictor of the postprandial response to a mixed meal. Carbohydrate dose, fiber, food structure and processing, protein, fat, meal sequence, gastric emptying, medication, physical activity, timing, and individual physiology can modify postprandial glycemia. Consequently, GI is most appropriately considered one characteristic of carbohydrate quality rather than a stand-alone meal-planning system.

CGM provides an increasingly practical means of characterizing individual responses to meals and lifestyle interventions. Nevertheless, the magnitude of an acute glucose excursion is not equivalent to the overall nutritional quality of a food or meal.

Conclusions

Nutrition management of T2D should move beyond binary classifications of carbohydrate-rich foods as beneficial or harmful and beyond reliance on a single numerical characteristic such as GI. Available evidence favors individualized dietary patterns that integrate carbohydrate quantity and quality, fiber, degree of processing, mixed-meal composition, medication use, cardiometabolic risk, cultural preferences, and sustainability. CGM may complement this approach by identifying individual glycemic responses, but isolated CGM responses should not be used as the sole basis for determining nutritional quality.

Keywords: type 2 diabetes mellitus; carbohydrate; postprandial glycemia; medical nutrition therapy; dietary fiber; glycemic index; glycemic load; mixed meals; continuous glucose monitoring; personalized nutrition

1. Introduction

Type 2 diabetes mellitus is a heterogeneous metabolic disorder characterized by varying combinations of insulin resistance, progressive β-cell dysfunction, altered hepatic glucose metabolism, and other disturbances contributing to chronic hyperglycemia. Nutrition therapy remains a central component of diabetes management alongside physical activity, diabetes self-management education and support, pharmacotherapy, and management of cardiovascular and other metabolic risk factors [1-4].

Despite decades of research, one of the most persistent questions in diabetes nutrition remains deceptively simple: what type and quantity of carbohydrate should a person with T2D consume?

Contemporary professional recommendations do not identify a single ideal distribution of carbohydrate, protein, and fat applicable to all people with diabetes. The 2026 ADA Standards of Care emphasize individualized medical nutrition therapy (MNT) and recommend consideration of nutrient quality, total energy intake, metabolic goals, and individual preferences rather than a universal macronutrient prescription [1]. European recommendations from the DNSG of the EASD similarly support a range of dietary approaches while emphasizing minimally processed plant foods, including whole grains, vegetables, whole fruits, legumes, nuts, and seeds [2]. AACE likewise places individualized nutrition within comprehensive diabetes care [4].

The clinical question extends beyond carbohydrate quantity. The glucose response to a carbohydrate-containing food is affected by the amount consumed, its physical structure and degree of processing, fiber content, accompanying protein and fat, meal sequence, gastric emptying, medication use, physical activity, timing of consumption, and individual metabolic characteristics. The postprandial response to a food consumed alone therefore cannot necessarily be extrapolated to the response produced when that food is incorporated into a mixed meal.

The increasing availability of CGM has made this complexity visible outside research laboratories. Individuals can now observe substantial differences in glucose responses among meals and, in some cases, between apparently similar exposures. This development offers opportunities for individualized MNT but also creates a risk of reducing nutritional quality to the magnitude of an acute glucose excursion.

This review examines contemporary evidence regarding dietary carbohydrates, mixed-meal composition, and postprandial glycemia in adults with T2D. Particular attention is given to the clinical interpretation of carbohydrate quality, GI and GL, fiber, protein and fat in mixed meals, nutrient sequence, meal timing, dietary patterns, and the emerging role of CGM-guided personalized nutrition.

2. Methods

This narrative review was designed to synthesize clinically relevant evidence published between January 2021 and September 2026 concerning dietary carbohydrate, meal composition, postprandial glycemia, and CGM-guided nutrition in adults with T2D.

PubMed/MEDLINE served as the principal bibliographic database. Search concepts included combinations of Medical Subject Headings (MeSH) and free-text terms relating to Diabetes Mellitus, Type 2, Diet Therapy, Carbohydrates, Dietary Fiber, Whole Grains, Glycemic Index, Blood Glucose, Postprandial Period, Eating, Continuous Glucose Monitoring, low-carbohydrate diets, Mediterranean dietary patterns, meal timing, meal sequence, and personalized nutrition.

Priority was given to systematic reviews and meta-analyses of randomized trials, followed by RCTs where recent syntheses were unavailable or where an emerging question required consideration of primary evidence. Contemporary recommendations from the ADA, EASD/DNSG, and AACE were used to contextualize clinical interpretation [1-4].

Human studies published in English and relevant to adults with T2D were prioritized. Animal and in vitro studies were excluded from the clinical synthesis. Publications before 2021 were not used as evidence for the conclusions of this review.

Because this is a narrative rather than systematic review, study identification and selection were directed by clinical relevance rather than a prospectively registered systematic-review protocol. Duplicate independent screening, formal study-level risk-of-bias assessment, and independent quantitative synthesis were not performed. Numerical estimates reported below are therefore derived from the cited publications and are presented to characterize the magnitude and direction of evidence rather than as independently calculated pooled effects.

3. Dietary Carbohydrate Quantity

Carbohydrate restriction remains one of the most extensively debated nutritional strategies in T2D. From an acute physiological perspective, reducing available carbohydrate can reduce the dietary glucose load and may attenuate postprandial glucose excursions. The clinical effectiveness of carbohydrate restriction over months or years, however, depends on considerably more than this immediate effect.

The ADA does not recommend a universal carbohydrate percentage for people with diabetes and emphasizes individualization of macronutrient distribution [1]. European recommendations similarly allow different dietary patterns rather than identifying one optimal carbohydrate prescription [2].

Recent systematic evidence illustrates why this distinction is necessary. An overview of systematic reviews published in 2025 concluded that evidence supporting low-carbohydrate interventions for metabolic control in T2D is heterogeneous, complicating their application as a universal prescription [5]. A 2025 systematic review and meta-analysis of 27 RCTs involving 2,870 participants found modest glycemic benefits from lower-carbohydrate interventions, with the greatest effects occurring over shorter periods and attenuation over longer follow-up [6].

Longer-term comparative evidence is less persuasive. A 2022 Cochrane review of low-carbohydrate versus balanced-carbohydrate weight-reducing diets included adults with and without T2D. Among participants with T2D, there was probably little or no difference between dietary approaches in body weight and several cardiovascular risk factors, including HbA1c, over one to two years [7].

These findings are not contradictory. A dietary intervention may improve glycemia during the initial months while providing little comparative advantage over another appropriately implemented dietary approach over longer periods. Adherence, weight change, energy intake, replacement macronutrients, medication adjustments, cultural compatibility, and dietary quality may influence outcomes.

The appropriate clinical question is therefore not whether all people with T2D should consume a predetermined amount of carbohydrate. Rather, carbohydrate intake should be individualized according to glycemic goals, medication regimen, dietary quality, cardiometabolic risk, preferences, cultural eating patterns, and the individual's ability to sustain the intervention.

4. Carbohydrate Quality and Food Processing

Carbohydrate quantity and carbohydrate quality are related but distinct considerations.

Contemporary ADA guidance emphasizes minimally processed, nutrient-dense, high-fiber carbohydrate sources, including nonstarchy vegetables, whole fruits, legumes, and whole grains [1]. European DNSG recommendations similarly prioritize minimally processed plant foods while recommending reduced consumption of refined grains and sugar-sweetened beverages [2].

This distinction has direct clinical implications. Whole fruit, legumes, intact whole grains, refined bread, confectionery, and sugar-sweetened beverages may all provide carbohydrate, but they differ substantially in fiber, food structure, micronutrient content, phytochemicals, energy density, degree of processing, and physiological effects.

Whole-grain research illustrates the relevance of food quality. A 2021 systematic review and meta-analysis of RCTs in people with diabetes reported improvements in fasting plasma glucose and HbA1c with whole-grain consumption, although substantial heterogeneity was present [8]. Another systematic review comparing whole with refined grains found improvements in postprandial glycemia and insulinemia and a modest improvement in HbA1c [9].

A broader 2024 systematic review and dose-response meta-analysis also reported modest favorable effects of whole-grain consumption on fasting glucose, although effects on HbA1c and insulin resistance were smaller and less certain [10].

Consequently, describing carbohydrate-containing foods solely according to total carbohydrate content provides an incomplete representation of their metabolic and nutritional characteristics.

5. Dietary Fiber

Dietary fiber represents one of the clearest examples of why carbohydrate quality cannot be inferred from carbohydrate quantity alone.

The ADA recommends emphasizing minimally processed, nutrient-dense, fiber-rich carbohydrate sources and a dietary fiber intake of at least approximately 14 g per 1,000 kcal [1]. European recommendations similarly emphasize whole grains, vegetables, whole fruit, legumes, nuts, and seeds [2].

A 2024 systematic review of dietary fiber interventions in T2D found that increasing fiber intake was associated with improvements in several metabolic outcomes, although substantial heterogeneity existed in fiber type, source, dose, intervention duration, and background diet [11].

More specific evidence is available for viscous soluble fiber. A 2023 systematic review and meta-analysis of RCTs reported reductions in HbA1c of 0.47 percentage points and fasting glucose of 0.93 mmol/L, equivalent to approximately 16.7 mg/dL, together with improvements in total and LDL cholesterol [12]. These results concern specific fiber interventions and should not be assumed to represent identical effects from every source or dose of dietary fiber.

The clinical significance of fiber also extends beyond a single glucose measurement. Naturally fiber-rich foods frequently contribute vitamins, minerals, phytochemicals, and other components of a high-quality dietary pattern. Thus, increasing fiber should generally be considered part of improving overall dietary quality rather than merely a technique for suppressing an acute glucose excursion.

6. Glycemic Index and Glycemic Load in the Context of Mixed Meals

GI provides a standardized measure of the relative postprandial glycemic effect of carbohydrate-containing foods, whereas GL incorporates both GI and the amount of available carbohydrate consumed. These measures provide information about carbohydrate quality and have demonstrated clinical relevance. Their usefulness in MNT, however, should be distinguished from their usefulness as stand-alone tools for constructing mixed meals.

Randomized intervention evidence indicates that lower-GI/GL dietary patterns can modestly improve glycemic control. A 2021 systematic review and meta-analysis of 29 trial comparisons involving 1,617 participants with diabetes reported that lower-GI/GL dietary patterns reduced HbA1c by 0.31 percentage points (95% CI, −0.42 to −0.19) compared with higher-GI/GL control diets [13]. Improvements were also observed in several secondary cardiometabolic outcomes, although substantial heterogeneity was present.

Thus, GI should not be dismissed as metabolically irrelevant. At the same time, evidence supporting lower-GI dietary patterns does not establish that the GI value of an individual food is a sufficient method for predicting the glucose response to the meal in which that food is consumed.

This distinction is particularly important because foods are rarely consumed as isolated carbohydrate sources. Postprandial glycemia following a mixed meal reflects interactions among the amount and characteristics of available carbohydrate, fiber, food structure and processing, protein, fat, portion size, gastric emptying, hormonal responses, meal sequence, medication use, physical activity, timing, and individual metabolic characteristics.

Accordingly, the glucose response to bread consumed alone should not automatically be assumed to be identical to the response when the same bread is consumed as part of a meal containing vegetables, protein, fat, and additional fiber. The bread retains its intrinsic GI classification, but the physiological exposure represented by the complete meal has changed.

The appropriate interpretation is therefore that meal composition modifies the postprandial glycemic response, not necessarily that another food has changed the intrinsic GI of the original carbohydrate source.

This distinction also prevents GI from being interpreted as a measure of overall nutritional quality. A smaller immediate glucose excursion does not necessarily identify a nutritionally superior meal. Dietary assessment must additionally consider fiber, nutrient density, fatty-acid composition, energy density, sodium, degree of processing, and the contribution of the meal to the overall dietary pattern.

GI may consequently provide useful supplementary information, particularly when comparing otherwise similar carbohydrate-containing foods or considering overall dietary patterns. It is substantially less informative when used alone to predict the response to complex mixed meals.

For MNT, GI and GL should therefore be considered alongside carbohydrate quantity, fiber, food structure and processing, portion size, complete meal composition, and individual metabolic response. Patients do not need to construct meals primarily by consulting GI tables. The complete meal and the individual's response to that meal are more clinically relevant than the GI value of any single component.

7. Whole Fruit: Why Carbohydrate Content Alone Is Insufficient

Whole fruit provides a useful clinical example of the limitations of classifying foods solely by carbohydrate or sugar content.

Fruit contains naturally occurring sugars but also water, fiber, micronutrients, phytochemicals, and a food matrix fundamentally different from sugar-sweetened beverages and isolated sugars. Current ADA and European recommendations include whole fruit among appropriate nutrient-dense foods [1,2].

A 2023 meta-analysis of 19 RCTs involving 888 participants with diabetes reported that fruit interventions reduced fasting glucose by approximately 8.4 mg/dL (0.47 mmol/L), whereas the pooled effect on HbA1c was not statistically significant [14]. The interventions were heterogeneous, and these findings should not be interpreted to mean that increasing fruit intake will necessarily lower glucose in every individual.

Rather, the evidence provides no basis for routinely excluding whole fruit from diabetes nutrition therapy merely because it contains carbohydrate.

Similarly, combining fruit with nuts, yogurt, or other foods creates a mixed meal or snack whose postprandial response may differ from that of the fruit consumed alone. The scientifically appropriate description is that meal composition may modify the glycemic response; it should not be described simply as changing the intrinsic GI of the fruit.

Within the 2021–2026 evidence window used for this review, evidence is insufficient to support a universal recommendation that whole fruit must routinely be combined with nuts or another specific food solely to reduce postprandial glucose. Such combinations may nevertheless be appropriate within individualized MNT for reasons including nutrient composition, satiety, preferences, and observed individual response.

8. Protein, Fat, and the Mixed-Meal Response

Most meals contain more than one macronutrient. Consequently, postprandial glucose cannot be understood solely from the carbohydrate component.

Protein can modify gastric emptying, insulin secretion, incretin responses, and postprandial glucose. A 2024 systematic review and meta-analysis of acute controlled feeding trials evaluated the addition of protein to carbohydrate-containing meals. Among adults with T2D, effects on glucose were smaller and less consistent than among metabolically healthy participants. Animal protein was associated with an approximately 13% reduction in glucose area under the curve but also a substantial increase in insulin response; dairy protein also reduced glucose exposure, with considerable heterogeneity among studies [15].

These findings caution against the simplified clinical statement that adding protein merely “lowers the GI” of carbohydrate. Protein modifies the physiological response to the complete meal, and the effect varies according to protein source, dose, meal composition, and metabolic status.

Dietary fat can similarly alter the timing of postprandial glucose appearance, in part through effects on gastric emptying. A lower or delayed early glucose excursion after adding fat should not, however, be interpreted automatically as an improvement in overall nutritional quality. Fat type, quantity, energy density, lipid effects, cardiovascular risk, and overall dietary pattern remain relevant.

Thus, reducing the immediate postprandial glucose peak cannot be the sole criterion for determining whether a mixed meal is nutritionally appropriate.

9. Nutrient Sequence

Nutrient sequence provides further evidence that the postprandial response to a meal cannot be predicted solely from the GI values of its individual components.

A 2026 systematic review and meta-analysis evaluated carbohydrate-last compared with carbohydrate-first or unordered consumption in adults with T2D. Seventeen studies involving 389 participants were included [16]. Carbohydrate-last consumption reduced postprandial glucose at 60 and 120 minutes and produced only a small reduction in HbA1c during follow-up. A correction to this publication was subsequently issued, which should be considered when interpreting its quantitative estimates.

The broader finding remains clinically relevant: altering the order in which the same macronutrients are consumed can modify the postprandial response without necessarily changing the foods themselves.

Several mechanisms may contribute, including altered gastric emptying and changes in incretin and insulin responses. Nevertheless, the evidence base remains relatively small, and many studies have been acute or short term.

Meal sequence may therefore represent a practical adjunct for selected individuals, but current evidence does not justify treating carbohydrate-last eating as a replacement for comprehensive MNT, appropriate pharmacotherapy, physical activity, or overall dietary quality.

10. Meal Timing and Chrononutrition

Glucose tolerance and metabolic responses vary across the day, providing a physiological rationale for examining meal timing independently of food composition.

A 2026 systematic review and meta-analysis of human intervention studies found that earlier compared with later meal intake reduced two-hour postprandial glucose by 1.51 mmol/L, equivalent to approximately 27.2 mg/dL, in short-duration studies [17]. However, most included interventions lasted no longer than one week, heterogeneity was high, and longer-duration studies did not establish a sufficiently robust advantage to support definitive clinical recommendations.

A six-month RCT published in 2024 compared time-restricted eating with individualized dietitian-led dietary guidance in adults with T2D and overweight or obesity. HbA1c decreased in both groups, without evidence establishing time-restricted eating as clearly superior to individualized dietetic practice [18].

Meal timing should consequently be regarded as a potentially useful individualized strategy rather than a universal requirement. Medication timing, hypoglycemia risk, occupation, sleep patterns, cultural practices, food access, and adherence may influence feasibility and safety.

11. Dietary Patterns: Moving Beyond Individual Nutrients

The focus on individual nutrients can obscure a consistent finding in contemporary nutrition research: several dietary patterns can support effective T2D management.

The EASD/DNSG recommendations recognize multiple appropriate dietary approaches and emphasize minimally processed plant foods rather than a single macronutrient distribution [2]. The ADA similarly recommends individualized meal plans emphasizing high-quality foods rather than prescribing one ideal carbohydrate, protein, and fat distribution [1].

A 2023 network meta-analysis of 42 RCTs involving 4,809 participants with T2D compared 10 dietary approaches. Several patterns improved glycemic outcomes, including Mediterranean, moderate-carbohydrate, lower-carbohydrate, low-GI, and other dietary approaches. Differences in body weight contributed to observed differences in glycemic outcomes, underscoring the difficulty of attributing effects exclusively to macronutrient distribution [19].

Mediterranean-style eating is particularly relevant because it demonstrates that a metabolically favorable dietary pattern does not need to be defined primarily by carbohydrate restriction. Its characteristic foods include vegetables, legumes, whole grains, fruit, nuts, seeds, and unsaturated fats.

The available evidence therefore favors flexibility within an evidence-based framework. The goal is not to identify a single universally superior named diet, but to construct a nutritionally adequate, sustainable pattern capable of meeting individual glycemic and cardiometabolic goals.

12. Continuous Glucose Monitoring and Personalized Nutrition

CGM has changed the clinical visibility of postprandial glycemia.

HbA1c provides an important measure of longer-term glycemic exposure but does not describe the timing, direction, or magnitude of individual glucose excursions. CGM can characterize mean glucose, glucose variability, time in range, time above range, and temporal responses to meals, physical activity, medication, sleep, and other behaviors.

This creates a potentially valuable tool for individualized nutrition counseling.

A 2024 systematic review and meta-analysis of RCTs evaluating CGM in people with T2D not using insulin reported an HbA1c reduction of approximately 0.31 percentage points and an increase in time in range of approximately 8.6 percentage points compared with control conditions [20].

More directly relevant to nutrition, a 2025 systematic review and meta-analysis evaluated CGM interventions designed to guide lifestyle choices, particularly nutrition. Twenty-one RCTs involving 2,734 adults were included, with 20 eligible for quantitative synthesis [21]. CGM-supported interventions were associated with a reduction in HbA1c of 0.46 percentage points and an increase of 7.18 percentage points in time in the 70–180 mg/dL (3.9–10.0 mmol/L) range. Time above 180 mg/dL (10.0 mmol/L) decreased by 7.32 percentage points, and fasting glucose decreased by approximately 7.9 mg/dL (0.44 mmol/L). Certainty of evidence varied among outcomes.

These results support CGM as a potentially useful feedback tool within comprehensive lifestyle and nutrition interventions. They do not establish that every postprandial excursion should be minimized or that foods should be ranked exclusively according to their CGM traces.

13. Why CGM Response Is Not Equivalent to Nutritional Quality

The distinction between glycemic response and nutritional quality is fundamental to appropriate interpretation of CGM.

CGM measures interstitial glucose. It does not directly measure dietary fiber, micronutrient adequacy, fatty-acid composition, protein quality, sodium intake, phytochemical exposure, degree of processing, satiety, gastrointestinal effects, or the long-term cardiovascular consequences of a dietary pattern.

Consequently, selecting foods solely according to the smallest postprandial glucose excursion could produce nutritionally undesirable choices.

For example, modifying a carbohydrate-containing meal by adding substantial fat may change the timing or magnitude of the early glucose response. Whether this represents a nutritionally favorable modification depends on the amount and type of fat, total energy intake, cardiometabolic context, and the remainder of the dietary pattern.

Conversely, a nutrient-dense carbohydrate-containing food may produce a measurable glucose excursion while contributing fiber, vitamins, minerals, and other desirable dietary components.

CGM should therefore be understood as providing an additional phenotype of dietary response rather than functioning as an independent nutritional rating system.

14. Interindividual Variation and Personalized Postprandial Responses

Personalized nutrition is partly motivated by the observation that individuals may differ in their postprandial responses to apparently similar meals.

The biological basis for such variation is plausible. Differences in insulin secretion and sensitivity, gastric emptying, medication use, physical activity, sleep, meal timing, prior meals, and other physiological and behavioral factors may influence glucose responses.

CGM allows these responses to be observed under free-living conditions. However, the observation that two individuals respond differently to the same meal does not by itself demonstrate that long-term clinical outcomes will improve when food selection is optimized to minimize each individual's postprandial excursions.

This distinction is central to evidence-based personalized nutrition. Prediction of a glucose response and demonstration of improved long-term clinical outcomes are separate evidentiary questions.

At present, CGM-guided nutrition is most defensible when used to complement established MNT principles. It may help identify repeated patterns, test clinically relevant hypotheses, and support behavior change while dietary quality, medication, cardiometabolic risk, preferences, and sustainability remain part of the interpretation.

15. Translating the Evidence Into Common Clinical Questions

The evidence reviewed above provides a framework for addressing frequently encountered questions without resorting to categorical food rules.

Should people with T2D avoid carbohydrates?No contemporary U.S. or European recommendation supports universal carbohydrate elimination. Carbohydrate amount should be individualized while dietary quality is emphasized [1,2].

How much carbohydrate should a person with T2D consume?No single percentage of energy or gram target has been established as optimal for all individuals. Glycemic goals, medication, energy requirements, food preferences, dietary quality, and sustainability should inform the prescription [1-4].

Are lower-carbohydrate diets effective?They can improve glycemic outcomes, particularly over shorter periods. Evidence for superiority over appropriately implemented balanced-carbohydrate approaches is less convincing at longer follow-up [5-7].

Should people with diabetes use GI tables to plan their meals?GI provides information about one characteristic of carbohydrate-containing foods, and lower-GI/GL dietary patterns can modestly improve glycemic control [13]. However, GI should not be used as a stand-alone meal-planning system because real-world mixed-meal responses depend on carbohydrate quantity, fiber, processing, protein, fat, portion size, meal sequence, and individual physiology.

Can people with T2D eat fruit?Whole fruit is included within contemporary high-quality dietary patterns, and recent randomized evidence does not support routine exclusion based solely on carbohydrate content [1,2,14].

Should fruit always be combined with nuts or protein?There is insufficient recent evidence to establish this as a universal requirement. Mixed-meal composition can modify the postprandial response, but food combinations should be individualized according to nutritional adequacy, preferences, satiety, medication, and observed metabolic response.

Does fiber matter?Yes. High-fiber foods are consistently emphasized in contemporary professional recommendations, and recent intervention evidence supports favorable effects of dietary fiber, including viscous soluble fiber, on glycemic outcomes [1,2,11,12].

Does adding protein reduce the glucose response to carbohydrate?Protein can modify acute glucose and insulin responses, but effects vary according to metabolic status, protein source, dose, and meal composition [15]. This does not support a universal rule that every carbohydrate food must be paired with additional protein.

Should carbohydrate be eaten last?Carbohydrate-last meal sequences can reduce acute postprandial glucose, but evidence for substantial long-term glycemic benefit remains limited [16].

Is eating earlier in the day metabolically preferable?Short-duration studies provide physiological evidence favoring earlier meal timing, but current long-term evidence is insufficient to support a universal timing prescription [17,18].

What is the best diet for T2D?No single dietary pattern is universally superior. Several dietary approaches can improve glycemic outcomes when appropriately implemented. Dietary quality, adherence, cultural suitability, cardiometabolic goals, and sustainability are central considerations [1,2,19].

Can CGM identify which foods are best for an individual?CGM can identify the glucose response to a meal and may support nutrition-related behavior change [20,21]. It cannot independently determine the overall nutritional quality of that meal.

16. Implications for Medical Nutrition Therapy

The principal implication for dietetic practice is that carbohydrate counseling should move beyond both restriction-based messaging and reduction of food quality to a single numerical characteristic.

A clinically useful assessment considers at least four dimensions: the quantity of available carbohydrate; the quality, structure, fiber content, and processing of the carbohydrate source; the composition of the complete meal; and the individual's metabolic response within the context of the overall dietary pattern.

Medication regimen is also essential. The nutritional implications of carbohydrate modification differ between an individual using medications with meaningful hypoglycemia risk and an individual whose treatment has little intrinsic hypoglycemia risk. Dietary advice should therefore be integrated with the medical treatment plan rather than provided in isolation.

CGM may strengthen this process when it is used to investigate repeated patterns rather than create rigid food rules. A recurrent postprandial excursion may prompt assessment of carbohydrate amount, food structure, fiber, meal composition, medication timing, or physical activity. The appropriate intervention cannot necessarily be inferred from the glucose trace alone.

This approach also avoids unnecessary moralization of food. A glucose excursion is physiological information rather than evidence that a food is intrinsically “good” or “bad.” MNT should translate metabolic information into clinically meaningful decisions while preserving nutritional adequacy, dietary flexibility, cultural relevance, and long-term sustainability.

17. Limitations of the Evidence and of This Review

Several limitations complicate interpretation of the literature.

Definitions of low-carbohydrate and very-low-carbohydrate diets differ among trials. Reported dietary prescriptions may also differ from actual intake, and comparator diets vary considerably.

Similarly, lower-GI interventions may differ from control diets in fiber, processing, food structure, and other characteristics. It is therefore difficult to attribute all observed effects exclusively to GI.

Acute feeding studies examining protein, fat, meal sequence, or timing cannot necessarily predict long-term HbA1c, cardiovascular outcomes, microvascular complications, or quality of life. An intervention capable of reducing a two-hour glucose excursion is not necessarily established as superior for long-term diabetes management.

Dietary trials are difficult to blind, adherence frequently changes over time, and improvements in body weight can mediate part of the observed glycemic effect. Medication adjustments may further complicate interpretation.

CGM-based personalized nutrition remains an evolving field. Improvements associated with CGM-supported interventions are clinically promising, but the independent contributions of personalized food selection, education, behavioral feedback, increased engagement, and other components remain incompletely resolved.

The present article is a narrative review rather than a systematic review. Although the evidence search was structured and restricted to contemporary sources, formal duplicate screening, prospectively registered eligibility criteria, independent risk-of-bias assessment, and de novo meta-analysis were not undertaken. Selection bias therefore cannot be excluded.

Finally, the deliberate restriction to publications from 2021 through 2026 improves contemporaneity but excludes older foundational physiological and clinical studies. Conclusions should therefore be understood as a synthesis of recent evidence and contemporary professional guidance rather than a complete historical review of the field.

18. Future Research

Several areas warrant further investigation.

First, longer-duration RCTs are needed to determine whether personalized modification of postprandial glucose responses provides benefits beyond conventional high-quality MNT.

Second, studies comparing different carbohydrate intakes should characterize not only the carbohydrate removed but also the foods and macronutrients replacing it. The metabolic implications of reducing carbohydrate cannot be separated from the nutritional composition of its replacement.

Third, research examining GI should distinguish the properties of isolated foods from the physiological responses to complete mixed meals. Studies should account for carbohydrate dose, fiber, processing, protein, fat, and meal structure rather than assuming that food-level GI alone predicts free-living postprandial responses.

Fourth, meal-sequence and chrononutrition research requires larger samples, longer interventions, and clinically meaningful outcomes rather than reliance primarily on acute glucose excursions.

Fifth, CGM-guided nutrition studies should evaluate outcomes beyond glucose, including dietary quality, lipids, blood pressure, medication requirements, hypoglycemia, body composition, quality of life, eating behavior, and cardiovascular risk.

Finally, personalized nutrition strategies should be evaluated in populations representing diverse ethnic, cultural, socioeconomic, and geographic contexts. An intervention that performs well in a narrowly selected research population should not automatically be assumed to generalize across the heterogeneous population living with T2D.

19. Conclusion

The relationship between dietary carbohydrate and glycemic control in T2D cannot be reduced to a universal carbohydrate target, a list of foods to avoid, or a numerical GI threshold.

Lower-carbohydrate approaches can improve glycemic outcomes, particularly over shorter periods, but contemporary evidence does not establish a single optimal carbohydrate intake for all adults with T2D. Carbohydrate quality remains fundamental. Minimally processed, nutrient-dense, fiber-rich foods—including vegetables, legumes, whole fruits, and whole grains—are consistently supported by contemporary U.S. and European professional recommendations.

GI and GL provide meaningful information about carbohydrate quality, and lower-GI/GL dietary patterns can modestly improve glycemic control. Their clinical value should nevertheless be interpreted within the context of real-world eating. Most foods are consumed as components of mixed meals, in which carbohydrate quantity, fiber, food structure and processing, protein, fat, portion size, meal sequence, and individual physiology collectively influence the postprandial glucose response. The GI of one component therefore provides only partial information about the metabolic response to the complete meal.

Similarly, a smaller postprandial glucose excursion should not automatically be interpreted as evidence of superior nutritional quality. Glycemia is an important clinical outcome, but it represents only one dimension of nutrition.

CGM offers an important opportunity to move from population averages toward observation of individual postprandial responses. Its most defensible role in nutrition therapy is complementary: CGM can help identify patterns, evaluate responses to complete meals, and support individualized behavior change, but it cannot independently determine whether a food or dietary pattern is nutritionally appropriate.

The contemporary approach to MNT in T2D should therefore integrate carbohydrate quantity, carbohydrate quality, food processing, fiber, complete meal composition, dietary pattern, treatment regimen, individual metabolic response, cultural context, and long-term sustainability. This framework is more clinically informative than carbohydrate restriction or GI classification alone and provides an evidence-based foundation for the responsible incorporation of CGM into personalized nutrition.

References

1. American Diabetes Association Professional Practice Committee for Diabetes. 5. Facilitating positive health behaviors and well-being to improve health outcomes: Standards of Care in Diabetes—2026. Diabetes Care. 2026;49(Suppl 1). doi:10.2337/dc26-S005.

2. Diabetes and Nutrition Study Group (DNSG) of the European Association for the Study of Diabetes (EASD). Evidence-based European recommendations for the dietary management of diabetes. Diabetologia. 2023;66(6):965-985. doi:10.1007/s00125-023-05894-8.

3. Davies MJ, Aroda VR, Collins BS, Gabbay RA, Green J, Maruthur NM, et al. Management of hyperglycemia in type 2 diabetes, 2022: a consensus report by the American Diabetes Association and the European Association for the Study of Diabetes. Diabetes Care. 2022;45(11):2753-2786. doi:10.2337/dci22-0034.

4. Blonde L, Umpierrez GE, Reddy SS, McGill JB, Berga SL, Bush M, et al. American Association of Clinical Endocrinology clinical practice guideline: developing a diabetes mellitus comprehensive care plan—2022 update. Endocr Pract. 2022;28(10):923-1049. doi:10.1016/j.eprac.2022.08.002.

5. Beretta MV, Flores CAO, Colameo GF, Echabe LW, Busnello FM. Low-carbohydrate dietary interventions for metabolic control in individuals with type 2 diabetes mellitus: an overview of systematic reviews. Nutr Rev. 2025;83(7). doi:10.1093/nutrit/nuae123.

6. Mongkolsucharitkul P, Surawit A, Pimsen A, Winitchayothin S, Pumeiam S, Pinsawas B, et al. Effectiveness of low-carbohydrate diets on type 2 diabetes: a systematic review and meta-analysis of randomized controlled trials in Eastern vs. Western populations. Diabetes Res Clin Pract. 2025;229:112464. doi:10.1016/j.diabres.2025.112464.

7. Naude CE, Brand A, Schoonees A, Nguyen KA, Chaplin M, Volmink J. Low-carbohydrate versus balanced-carbohydrate diets for reducing weight and cardiovascular risk. Cochrane Database Syst Rev. 2022;1(1). doi:10.1002/14651858.CD013334.pub2.

8. Xu D, Fu L, Pan D, Lu Y, Yang C, Wang Y, et al. Role of whole grain consumption in glycaemic control of diabetic patients: a systematic review and meta-analysis of randomized controlled trials. Nutrients. 2022;14(1):109. doi:10.3390/nu14010109.

9. Whole grain intake, compared to refined grain, improves postprandial glycemia and insulinemia: a systematic review and meta-analysis of randomized controlled trials. Crit Rev Food Sci Nutr. 2021. doi:10.1080/10408398.2021.2017838.

10. Ying T, Zheng J, Kan J, Li W, Xue K, Du J, et al. Effects of whole grains on glycemic control: a systematic review and dose-response meta-analysis of prospective cohort studies and randomized controlled trials. J Health Popul Nutr. 2024;43:47. doi:10.1186/s41043-024-00542-y.

11. Nitzke D, Czermainski J, Rosa C, Coghetto C, Fernandes SA, Carteri RB. Increasing dietary fiber intake for type 2 diabetes mellitus management: a systematic review. World J Diabetes. 2024;15(5):1001-1010. doi:10.4239/wjd.v15.i5.1001.

12. Lu K, Yu T, Cao X, Xia H, Wang S, Sun G, et al. Effect of viscous soluble dietary fiber on glucose and lipid metabolism in patients with type 2 diabetes mellitus: a systematic review and meta-analysis on randomized clinical trials. Front Nutr. 2023;10:1253312. doi:10.3389/fnut.2023.1253312.

13. Chiavaroli L, Lee D, Ahmed A, Cheung A, Khan TA, Blanco Mejia S, et al. Effect of low glycaemic index or load dietary patterns on glycaemic control and cardiometabolic risk factors in diabetes: systematic review and meta-analysis of randomised controlled trials. BMJ. 2021;374. doi:10.1136/bmj.n1651.

14. Ren Y, Sun S, Su Y, Ying C, Luo H. Effect of fruit on glucose control in diabetes mellitus: a meta-analysis of nineteen randomized controlled trials. Front Endocrinol (Lausanne). 2023;14:1174545. doi:10.3389/fendo.2023.1174545.

15. Wolever TMS, Zurbau A, Koecher K, Au-Yeung F. The effect of adding protein to a carbohydrate meal on postprandial glucose and insulin responses: a systematic review and meta-analysis of acute controlled feeding trials. J Nutr. 2024;154(9):2640-2654. doi:10.1016/j.tjnut.2024.07.011.

16. Saldarriaga-Callejas LM, Ratan P, Pasqualotto E, Kodalak S, Bovi T, Trevisan T. Nutrient intake order on metabolic outcomes in type 2 diabetes: a systematic review and meta-analysis. Acta Diabetol. 2026;63(3):399-411. doi:10.1007/s00592-025-02586-0. Correction published 2026. doi:10.1007/s00592-026-02788-0.

17. Slebe R, Wenker E, Schoonmade LJ, Blondin DP, Campbell DJT, Carpentier AC, et al. Effects of timing of meal intake on glucose metabolism: a systematic review and meta-analysis of human intervention studies. Nutr Metab Cardiovasc Dis. 2026:104878. doi:10.1016/j.numecd.2026.104878.

18. Parr EB, Radford BE, Hall RC, Steventon-Lorenzen N, Flint SA, Siviour Z, et al. Comparing the effects of time-restricted eating on glycaemic control in people with type 2 diabetes with standard dietetic practice: a randomised controlled trial. Diabetes Res Clin Pract. 2024;217:111893. doi:10.1016/j.diabres.2024.111893.

19. Jing T, Zhang S, Bai M, Chen Z, Gao S, Li S, et al. Effect of dietary approaches on glycemic control in patients with type 2 diabetes: a systematic review with network meta-analysis of randomized trials. Nutrients. 2023;15(14):3156. doi:10.3390/nu15143156.

20. Ferreira ROM, Trevisan T, Pasqualotto E, Chavez MP, Marques BF, Lamounier RN, et al. Continuous glucose monitoring systems in noninsulin-treated people with type 2 diabetes: a systematic review and meta-analysis of randomized controlled trials. Diabetes Technol Ther. 2024;26(4):252-262. doi:10.1089/dia.2023.0390.

21. Bannuru RR, Bellini NJ, Bergenstal RM, Beverly EA, Christofides EA, Cox D, et al. Continuous glucose monitoring to guide lifestyle choices with a focus on nutrition in the management of type 2 diabetes: a systematic review and meta-analysis. J Diabetes Sci Technol. 2025 Oct 18:19322968251384318. doi:10.1177/19322968251384318. Online ahead of print.