Influence Of Diet And Metabolic Factors On Body Mass Index In Overweight And Obese Adults

PURPOSE: The purpose of this study was to explore the influence of dietary nutrients and blood borne metabolic variables on body mass index (BMI) in overweight and obese adults after participating in a 60-day lower calorie nutrient-rich diet plan or a usual care diet. METHODS: A 60-day follow-up was conducted to assess participant dietary intake (calories, protein, carbohydrate, fiber, sugar, fat, vitamin C, vitamin D), as well as blood glucose, insulin, and cholesterol. The Active Nutrition diet included 2 meal replacement shakes, an electrolyte replacement drink, a metabolic renewal supplement, one whole food meal, and 3-5 servings of whole food snacks (e.g., vegetables and fruits) daily, which totaled approximately 1200-1600 calories. Two stepwise multiple linear regressions were used to identify the most significant predictors of BMI for the Active Nutrition and control groups after adhering to the specified diet-plan for 60 days. RESULTS: Among the 60 participants, 49 were women and 11 were men, with a mean age of 38 ± 12 years. At 60 days post-intervention, the Active Nutrition group had an average BMI of 32.07 ± 3.56, an average fasting insulin level of 18.64 ± 11.65 μU/mL, and an average daily vitamin D intake of 10.68 ± 2.31 mcg. In comparison, the control group had a BMI of 33.23 ± 3.08, a fasting insulin level of 28.68 ± 17.0 μU/mL, and a vitamin D intake of 3.03 ± 2.36 mcg. Results of the multiple linear stepwise regression analyses indicated that in the group adhering to the Active Nutrition plan, both insulin (β = 0.38; p = .03) and vitamin D (β = -0.38; p = .03) levels significantly explained 34.1% of the variance of BMI (p = .004). In contrast, within the control group, only insulin (β = 0.58; p = .003) emerged as a significant predictor of BMI, explaining 33% of the variance (p = .003). No other dietary or metabolic variable had a significant influence on BMI, in either group (p > .05). CONCLUSIONS: In the present study, insulin was the main predictor of BMI in overweight and obese adults, with vitamin D contributing significantly in the Active Nutrition group. A decrease in insulin and an increase in vitamin D from pre- to post-intervention in the Active Nutrition group was also associated with a decrease in BMI, suggesting that vitamin D may work synergistically with insulin to support BMI reduction. Supported by: USANA Health Sciences sponsored research grant.