Yishai Zohar

Efforts to identify a preferable diet for weight management based on macronutrient composition have largely failed, but recent evidence suggests that satiety effects of carbohydrates may depend on the individual’s insulin-mediated cellular glucose uptake. Therefore, using data from the POUNDS LOST trial, pre-treatment fasting plasma glucose (FPG), fasting insulin (FI), and homeostatic model assessment of insulin resistance (HOMA-IR) were studied as prognostic markers of long-term weight loss in four diets differing in carbohydrate, fat, and protein content, while assessing the role of dietary fiber intake. Subjects with FPG p = 0.003) kg more on the low-fat/high-protein (n = 132) compared to the low-fat/average-protein diet (n = 136). Subjects with HOMA-IR ≥4 lost 3.6 (95% CI 0.2;7.1, p = 0.038) kg more body weight on the high-fat/high-protein (n = 35) compared to high-fat/average-protein diet (n = 33). Regardless of the randomized diet, subjects with prediabetes and FI below the median lost 5.6 kg (95% CI 0.6;10.6, p = 0.030) more when consuming ≥35 g (n = 15) compared to n = 16). Overall, subjects with normal glycemia lost most on the low-fat/high-protein diet, subjects with high HOMA-IR lost most on the high-fat/high protein diet, and subjects with prediabetes and low FI had particular benefit from dietary fiber in the diet.

The interaction between fasting plasma glucose (FPG) and fasting insulin (FI) concentrations and diets with different carbohydrate content were studied as prognostic markers of weight loss as recent studies up to 6 months of duration have suggested the importance of these biomarkers. This was a retrospective analysis of a clinical trial where participants with obesity were randomized to an ad libitum low-carbohydrate diet or a low-fat diet with low energy content (1200–1800 kcal/day [≈ 5.0–7.5 MJ/d]; ≤ 30% calories from fat) for 24 months. Participants were categorized (pretreatment) as normoglycemic (FPG < 5.6 mmol/L) or prediabetic (FPG ≥ 5.6–6.9 mmol/L) and further stratified by median FI. Linear mixed models were used to examine outcomes by FPG and FI values. After 2 years, participants with prediabetes and high FI lost 7.2 kg (95% CI 2.1;12.2, P = 0.005) more with the low-fat than low-carbohydrate diet, whereas those with prediabetes and low FI tended to lose 6.2 kg (95% CI −0.9;13.3, P = 0.088) more on the low-carbohydrate diet than low-fat diet [mean difference: 13.3 kg (95% CI 4.6;22.0, P = 0.003)]. No differences between diets were found among participants with normoglycemia and either high or low FI (both P ≥ 0.16). Fasting plasma glucose and insulin are strong predictors of the weight loss response to diets with different macronutrient composition and might be a useful approach for personalized weight management.

During the past several decades, numerous trials have compared various diets for the management of overweight and obesity, assuming that a single dietary strategy would be appropriate for all individuals. These studies have failed to provide strong evidence for the efficacy of any particular diet, and it is likely that different people will have different levels of success on different diets. We identified studies investigating pretreatment glycemia or insulinemia status, or both, of the individual as prognostic markers of weight loss during periods in which the composition of a participant's diet was known. Overall, research suggests that providing specific diets for weight management based on pretreatment glycemia and insulinemia statuses holds great promise for advancing personalized nutrition.