Dietary Macronutrient Intake and Changes in Body Composition: Impact on Indices of Cardio-Metabolic Health in Overweight/Obese Adults

Akua Frempomah Amankwaah, Purdue University

Abstract

The prevalence of type 2 diabetes as well as its major risk factor, obesity, is rapidly rising. Dietary modification is one of the cornerstones for prevention of type 2 diabetes. Extensive evidence indicates that higher dietary protein and fiber intakes independently blunt postprandial glucose and insulin, particularly dietary fiber. However, the extent to which the effects of protein and fiber intakes on postprandial glucose when co-consumed may be additive are uncertain, particularly in overweight individuals, who may be at risk of developing T2D. While weight loss is a well-established treatment for obesity, sustained weight control or maintenance may be a prevention strategy for obesity and its related morbidities. Extensive and consistent data supporting the impact of changes in body mass and body composition on changes in cardio-metabolic health indices during moderate or significant weight changes are available. Less is known whether, in the absence of clinically defined weight changes (> ± 5% body mass change), body composition changes within this range of weight stability predict changes in cardio-metabolic indices and whether total protein intake influences these associations. Expanding knowledge on the efficacy and effectiveness of intakes of higher protein and fiber on glycemic and insulinemic responses as well as assessing the predictive effect of changes in body mass and body composition on changes in cardio-metabolic indices during weight stability would promote prevention of type 2 diabetes and obesity, respectively. To this end, we conducted three studies briefly summarized herein. The purpose of study 1 was to conduct a randomized controlled intervention to assess the individual and combined effects of higher intakes of dietary protein and fiber on postprandial serum glucose and insulin responses. In addition, continuous glucose monitoring (CGM) was also used to assess the impact of the prolonged effect of dietary protein and fiber intakes on daily interstitial glucose concentrations. Overweight, young adults with normal glucose tolerance status were included in the study. We hypothesized that co-consumption of higher quantities of protein and fiber at breakfast would lower postprandial glucose and 24-h glucose responses. We observed that the intake of higher amounts of fiber or higher protein and fiber combined attenuated postprandial insulin and postprandial interstitial glucose, but the attenuation by higher fiber intake only was significant. Our results indicated that doubling the amount of protein from 12.5 g to 25 g/meal and quadrupling fiber from 2 to 8 g/meal at breakfast was not an effective strategy for modulating insulin-mediated glucose responses in young, overweight adults. Future studies could focus on assessing the long-term effects of this dietary strategy in overweight or obese adults with overt impaired glucose tolerance status. Studies 2 and 3 were secondary analyses with purposes to analyze data from a randomized control trial designed to assess the effects of whey protein supplementation on exercise training-induced changes in body composition and indices of metabolic syndrome in middle-aged adults with excess weight and obesity. In both studies, we assessed associations between changes in body composition and changes in cardio-metabolic health indices within a range of weight stability. The influences of dietary protein on the associations between changes in body composition and changes in cardio-metabolic health indices were also assessed in study 3. We hypothesized that within < ± 5% weight change, changes in body composition would predict changes in cardio-metabolic health indices with exercise training. Further, we hypothesized that higher total protein intake would predict exercise-induced body composition changes, but not cardio-metabolic health indices. In addition, controlling for total protein intake would abolish associations between changes in body composition and cardio-metabolic indexes. We found that changes in body fat, but not lean mass was associated with changes in whole-body insulin sensitivity index, HDL cholesterol, and waist circumference, but not fasting blood pressure, glucose, insulin, HOMA-IR, total cholesterol, LDL cholesterol, or triglycerides independent of total protein intake in weight-stable overweight/obese adults. Results from studies 2 and 3 collectively suggest that people with obesity should be encouraged to continue exercise training when meaningful weight loss is not achieved because of the potential beneficial impact of body composition changes on indexes of cardio-metabolic health.

Degree

Ph.D.

Advisors

Campbell, Purdue University.

Subject Area

Nutrition

COinS