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Intermittent energy restriction has become a popular method for the management of obesity. It is however a very old concept, although not always used specifically for weight loss, a good example being the Ramadan fast. While the Ramadan fast has been shown to lead to weight loss, the assessment of body composition changes may be another important consideration. Chapter 2 therefore assesses the effect of the Ramadan fast on body composition via a systematic review and meta-analysis. This showed that the Ramadan fast caused a decrease in all parameters of body composition. Subgroup analyses showed a significant decrease in fat percentage only in people with overweight or obesity. In studies used for the above review on the Ramadan fast, various methods are used to track body composition, a clear majority of them using bioelectrical impedance scales. These scales are commonly used due to them being a cheap, quick and easy method. Their ubiquitous use makes it important to understand their reliability. It has been suggested that rate of weight loss could possibly influence the utility of the scales. In Chapter 3, this was addressed by comparing the body composition measurements obtained by the scales to the 4-compartment model (a gold-standard for body composition measurement), both before and after a diet plan involving either FAST or SLOW weight loss for 16 weeks. We found that for individuals, the scales were generally inaccurate and imprecise, especially after weight loss (regardless of rate). In groups, the scales were much more reliable, with comparisons of the means and standard deviations of the scales versus the 4-compartment model showing no significant difference across all analyses. These results highlight that bioelectrical impedance scales may not be ideal for measuring body composition in individuals, although they may be suitable for use in groups, for instance, in the case of the Ramadan studies utilized in Chapter 2.

Stress and high-calorie diets increase the risk of developing metabolic syndrome. Glycyrrhizic acid (GA) has been shown to improve dyslipidaemia in rats fed on a high-calorie diet. This study aimed to examine the effects of GA on lipid metabolism in rats exposed to short- or long-term stress and on a high-calorie diet. The parameters examined included serum lipid profiles, serum free fatty acids and fatty acid profiles in tissues, and expression of peroxisome proliferator-activated receptors (PPAR), lipoprotein lipase (LPL), elongases and desaturases. Within the 14- or 28-day exposure groups, neither stress nor GA affected the lipid profile and serum free fatty acids. Stress did not affect PPAR-α expression in both the 14- and 28-day exposure groups. However, GA-treated rats from the former group had increased PPAR-α expression only in the kidney while all other tissues from the latter group were unaffected. Stress increased PPAR-γ expression in the heart of the 28-day exposure group but its expression was unaffected in all tissues of the 14-day exposure group. GA elevated PPAR-γ expression in the kidney and the skeletal muscles. Neither stress nor GA affected LPL expressions in all tissues from the 14-day exposure group but its expressions were elevated in the QF of the stressed rats and heart of the GA-treated rats of the 28-day exposure group. As for the elongases and desaturases in the liver, stress down-regulated ELOVL5 in the long-term exposure group while up-regulated ELOVL6 in the short-term exposure group while hepatic desaturases were unaffected by stress. Neither elongase nor desaturase expressions in the liver were affected by GA. This research is the first report of GA on lipid metabolism under stress and high-calorie diet conditions and the results gives evidence for the role of GA in ameliorating MetS via site-specific regulation of lipid metabolism gene expressions and modification of fatty acids.

Stress and high-calorie diet increase the risk of developing metabolic syndrome. Glycyrrhizic acid (GA) has been shown to improve hyperglycaemia and dyslipidaemia under various physiological conditions. This study was aimed at examining the effects of stress and GA on glucose metabolism under short- or long-term stress. Forty-eight Sprague Dawley rats were divided into two groups with constant stress induced by light (300-400 lux) for either 14 days (short-term stress) or 28 days (long-term stress). Within each group, the rats were subdivided into three treatment groups i.e. Group A (control group): high-calorie diet (HCD) only; Group B: HCD + stress (14 or 28 days) and Group C: HCD + stress (14 or 28 days) + GA (100 mg/kg). The blood glucose concentrations of the rats exposed to 14-day stress were elevated significantly and GA lowered blood glucose concentration significantly in the 14-day exposure group. The 28-day exposure group adapted to stress as shown by the lower adrenaline level and gluconeogenic enzymes activities in most of the tissues than the 14-day exposure group. With regards to adrenaline and corticosterone, GA was found to increased adrenaline significantly in the short-term exposure group while lowering corticosterone in the long-term exposure group. GA-treated short- and long-term exposure groups had significant reduction in hexose-6-phosphate dehydrogenase activities in the visceral adipose tissues and quadriceps femoris respectively. The results may indicate the role of GA in improving blood glucose concentration in individuals exposed to short-term stress who are already on a high-calorie diet via selective action on gluconeogenic enzymes in different tissues.