Severe energy restricted diet followed by a weight maintenance program does not increase appetite after weight loss in overweight and obese adults

Abstract

Introduction The prevalence of overweight and obesity has become a major health problem in the prediabetes and elderly populations, particularly among post-menopausal women. Weight loss treatment in post-menopausal women has potential benefits in relation to physical function, quality of life and reducing the medical complications associated with obesity. It is also beneficial in the prediabetes population in relation to glycaemic control, insulin sensitivity, dyslipidaemia and reducing blood pressure. In clinical practice, the most common non-surgical treatment for obesity is diet, whether it is a moderate or severe energy-restricted diet. Moderate energy restriction produces modest weight loss with an increase in appetite over baseline in overweight and/or obese individuals, while severe energy restriction is increasingly being used for the treatment of obesity due to the failure of more moderately energy-restricted diets to produce clinically significant weight loss and reduce hunger in the general overweight or obese population. Despite the benefits of severe energy restriction, it has been shown that, on resumption to a higher energy weight maintenance diet normal food intake, there is an increase in appetite which prevents ongoing weight loss and promotes weight regain. However, increase in appetite has been observed in overweight or obese people following either level of energy restriction. Hence, it remains unclear whether the increase in appetite is greater in response to severe or moderate energy restriction. This increase in appetite among overweight and/or obese individuals may prevent ongoing weight loss and promote weight regain. Yet very little appears to be known about the effect of severe dietary energy restriction on appetite in overweight and obese pre-diabetes or post-menopausal individuals. Further investigation is therefore required to determine the effect on appetite of severe energy restriction-induced weight loss followed by a weight maintenance program in this population. The present study aimed to assess: • the effects of severe energy restriction versus moderate energy restriction on appetite perception in obese post-menopausal individuals. • the effects of severe energy restriction followed by a weight maintenance program on appetite perception in overweight or obese pre-diabetes adults. Methods As explained in Chapter 2, 14 obese post-menopausal women aged 45-65 years with body mass index (BMI) between 30-40 kg/m2 were randomised into a 16 week severe energy-restricted diet (65-75% energy deficit from baseline energy intake) followed by 10 weeks of moderate energy restriction (35-45% of energy deficit from baseline energy intake) or a 26 week continuous moderate energy restriction regimen. At baseline (week 0), week 16 and week 26, we examined body weight, fasting and postprandial appetite as well as fasting circulating ketones for both diet groups. As described in Chapter 3, 70 overweight and obese pre-diabetic men and women aged 25-70 years with BMI ≥ 25 kg/m2 were investigated to determine the effect of an 8 week severe energy restriction diet followed by an 18 week weight maintenance program on body weight and fasting appetite (measured using visual analogue scales) at baseline (week 0), week 8 and week 26. Results The results in Chapter 2 showed that a 16-week severe energy restriction period followed by a 10-week moderate energy-restricted diet resulted in significant reduction in initial body weight (more than 20% of initial weight) without altering appetite in obese post-menopausal women. During the severe energy-restricted diet, fasting blood ketone levels were significantly increased (between week 0 and week 16) and reduced during the 10-week moderate energy-restricted diet. On the other hand, 26-week continuous moderate energy-restriction produced lower weight loss (6.4% of initial weight) with increased appetite and no changes in circulating ketones. These results suggest that the use of a severe energy restriction diet followed by a moderate energy restriction weight loss diet is relatively beneficial in terms of greater weight loss without an increase in appetite. The results in Chapter 3 showed that an 8 week severe energy-restricted diet followed by an 18 week weight maintenance program produced a significant reduction in initial body weight (15.5% of initial weight) with reduced fasting hunger; however fasting scores for desire to eat, prospective food consumption and fullness were unchanged from baseline. These results suggest that the use of a severe energy-restricted weight loss diet followed by a weight maintenance program is beneficial from the perspective of considerable weight loss and reduced hunger. Conclusion The findings from these two trials suggest that there are no disadvantages in losing weight rapidly via severe energy restriction in terms of appetite rebound. In Chapter 2 it is suggested that faster weight loss is advantageous as it gets weight off quickly without significant changes in appetite. At the same time, Chapter 3 suggests that a severe energy-restricted diet followed by a weight maintenance program is also beneficial as it produces a persistent decrease in hunger sensation that results in sustainable weight loss. Thus, it is concluded that both these weight loss interventions (a severe energy restriction weight loss diet followed by a moderate energy restriction diet or a severe energy restriction weight loss diet followed by a weight maintenance program) are beneficial for clinically relevant weight loss because they support better appetite control.