Factors predicting weight loss maintenance in overweight pre-diabetic adults. Differences in satiety levels in high protein or high carbohydrate diets and effect on weight loss maintenance.

Abstract

Background. Obesity is now a worldwide epidemic which largely results in deadly comorbidities such as Type 2 Diabetes. The best composition of diet for the prevention and management of obesity is relatively unknown, with the most effective weight loss maintenance approach widely debated. Aim. As a sub-study of a long-term three year diet and exercise intervention in the PREVIEW trial to investigate the effect of higher protein versus higher carbohydrate diets in a subgroup of 58 overweight adults. Specifically to investigate which factors predict long term weight loss maintenance by (i) investigating the impact of a higher protein / lower glycaemic index diet versus moderate protein / moderate GI diet on satiety levels and energy intake; and (ii) to identify any effects of gender, age group or physical activity in weight loss maintenance. Methodology. Overweight (BMI ≥25kg/m²) individuals with impaired glucose metabolism completed an 8 week low energy diet and 18 week weight loss maintenance phase in a 6 month intervention. Those who achieved ≥8% weight loss after low energy diet (LED) were randomised to one of two low-fat (<30% en) diet interventions: Higher protein (25%en intake protein), lower GI (<55) or moderate protein (15%en intake), moderate GI (>55); and also to one of two exercise interventions: High intensity (75mins vigorous exercise / week) or moderate intensity (150mins moderate exercise / week). Food diaries to assess energy intake were recorded at baseline and 6 months; weight, dual x-ray body scans and visual analogue scale (VAS) satiety questionnaires (hunger, satiated, fullness, desire to eat) were analysed at baseline, 8 weeks (post LED) and 6 months. Results. Of the 136 that were randomised, 58 individuals achieved 8% weight loss and completed all dietary records and questionnaires up to 6 months. Only the higher protein group significantly reduced energy intake from baseline to 6 months (p<0.0001), and there was no significant difference between the higher protein and moderate protein groups. In all subjects, a significant relationship was seen between hunger and EI (p=0.0430) and fullness and EI (p=0.0182). No significant difference in VAS changes were observed between baseline and 6 months in hunger, fullness, satiation in either the higher protein or moderate protein groups. Significant decrease in desire to eat from baseline to 6 months occurred in the HP group only (p=0.0200). No significant difference in weight change was seen between the high and moderate intensity exercise groups (p=0.6347). Both the higher and moderate protein groups maintained weight loss (within ±1kg) from post LED weight to 6 months, but no significant difference was observed between the higher and moderate protein groups in weight loss during the low energy diet or between the 18 weeks of weight maintenance. Discussion. Satiety measurements varied with the methods of analysis – food records indicated a higher protein diet decreased energy intake compared to baseline, but the VAS assessment did not show significant changes in hunger and / or fullness. Both low fat diets were effective at maintaining LED induced weight loss over 6 months, hence in this subgroup analysis of n=58 adults, no diet was better for weight loss maintenance, however further results from the long-term follow up of the participants will help to inform the lifestyle and diet recommendations best for achieving weight loss maintenance. Key words Weight loss, protein, weight loss maintenance, satiety.