Fiber Intake, Dietary Energy Density, and Diet‐Type Predict 6‐Month Weight‐Loss in Free‐Living Adults Who Adhered to Prescribed Macronutrient and Energy Composition of Varying Diets

Abstract

Diets are often designed to meet prescribed macronutrient targets; but the question persists as to whether free‐living individuals can actually achieve the specified levels. The POUNDS LOST study was a randomized clinical trial which examined the effects of four calorie‐restricted diets of varying macronutrient composition on weight loss in free‐living adults with obesity. The objective of this analysis was to identify predictors of weight loss after 6 months in participants who adhered to energy and macronutrient assignments. Energy adherence was defined as consuming within ± 10% of the target energy goal. Diet adherence was defined as consuming within ± 5% of the target macronutrient composition for fat and protein. Participants were randomized to receive one of four diets: 20% fat, 15% protein (low‐fat, average‐protein) 20% fat, 25% protein (low‐fat, high‐protein) 40% fat, 15% protein (high‐fat, average‐protein) 40% fat, 25% protein (high‐fat, high‐protein). Only 46 (13.3%) of the 345 participants who provided follow‐up data (61% male, 93% Caucasian) met the criteria for adherence to both energy and macronutrient targets. To identify variables associated with weight loss, a multiple regression model with a backward selection was fit and variables were retained if they met the p < 0.05 threshold. The returned variables included diet type (p = 0.056), energy density change from baseline (kcal/g) to the six‐month follow‐up (p < 0.0001), and fiber intake (g) (p < 0.0001). The effect of energy density varied across each level of diet assignment (p = 0.009). Interaction terms were explored. The final model explained 68.9% of the variance in weight change with the strongest predictor of weight change being dietary fiber; a 10g increase in dietary fiber consumption was associated with an average 3.7kg weight loss, independent of energy density and diet assignment. A decrease in energy density was positively associated with weight change for each diet‐type; however, this effect was most profound in the high‐fat, average‐protein diet. These results suggest that dietary factors may positively influence weight loss in addition to energy intake and macronutrient composition.Support or Funding InformationFunded by NIH‐NHLBI. ClinicalTrials.gov number, NCT00072995.