Nutritional and surgical influences on appetite regulation and body composition in overweight and obese humans

Abstract

In the present context of worldwide-prevalent obesity, optimisation of existing weight loss strategies and development of novel population-wide interventions is critical. Roux-en-Y gastric bypass (RYGB) is considered the gold-standard treatment for obesity. Weight loss is recommended prior to surgery to reduce liver size and risks of complications. However, little is known regarding the optimal pre-operative diet type and duration. In a first investigation, I examined the effect of three pre-operative diets on liver fat content (IHCL), as a proxy of liver volume, in obese patients undergoing RYGB. I compared the effects of a 2-week and 6-week liquid formula 800kcal/day low-calorie diet (LCD) with a low-carbohydrate, high-protein 1000kcal/day conventional food diet (control) prescribed routinely in bariatric clinics. The 2-week and 6-week LCD induced a 40% and 67% reduction in IHCL respectively compared with the control diet, which did not induce any significant loss in IHCL. In the overweight population, dietary changes remain the first-line treatment strategy to induce weight loss. Certain food components promote satiety by altering gastro-intestinal (GI) hormone release, and may therefore play a role in the prevention of obesity and type-2 diabetes mellitus (T2DM). Mycoprotein, a novel fungal food containing protein and fibre, reduces energy intake acutely and improves glucose homeostasis in lean individuals. In a second investigation, I explored the effect of mycoprotein on energy intake, glucose homeostasis, and GI hormones release in overweight volunteers. Mycoprotein significantly reduced acute energy intake by 10% compared with chicken in overweight individuals, without significantly altering GI hormones, and gastric emptying. Furthermore, mycoprotein reduced post-prandial insulin and improved insulin sensitivity compared with chicken, showing its potential health benefit in overweight individuals. These studies suggest that a 2-week pre-operative LCD may be optimal in the preparation for RYGB and that mycoprotein might be of benefit in the dietetic prevention of obesity and T2DM.