Energy Expenditure and Hormone Responses in Humans After Overeating High-Fructose Corn Syrup Versus Whole-Wheat Foods

Changes in serum cortisol levels after 10 days of overfeeding and fasting

Chronic caloric deprivation and obesity are complicated by hypercortisolemia. The effects of acute overfeeding and fasting on circulating free cortisol levels and conversion of cortisone to free cortisol are unknown. We hypothesized that serum-free cortisol and free cortisol-to-cortisone ratio would increase after both overfeeding and fasting. This is a prospective study of 22 healthy volunteers who completed a 10-day high-calorie protocol followed by a 10-day fast, separated by a 2-wk washout. Morning free and total cortisol and free cortisone levels (LC/MS) were measured at baseline and after 10 days of each intervention. Both high-calorie feeding and fasting increased total and free cortisol and the free cortisol-to-free cortisone ratio (P = 0.001 to P = 0.046). There were sex interactions, with significant effects in men (P < 0.001), but not in women (P = 0.898 and 1.000, respectively) in subset analyses examining the effects of fasting on free cortisol and the free-to-total cortisol ratio. Overfeeding and fasting both increase circulating free cortisol levels and appear to alter the balance between cortisol and its inactive metabolite, cortisone. Further study is warranted to determine whether elevated cortisol levels contribute to complications of starvation and obesity, such as bone fragility.NEW & NOTEWORTHY Overfeeding and fasting both increase circulating free cortisol levels and appear to alter the balance between cortisol and its inactive metabolite, cortisone. The effect of fasting on free cortisol levels is modified by sex. Further study is needed to determine the mechanisms driving the increases in cortisol.

Effects of Dietary Carbohydrate Profile on Nocturnal Metabolism, Sleep, and Wellbeing: A Review

Sleep is a crucial biological function and a well-established driver of health and wellbeing across the lifespan. In this review, we describe how sleep in humans is associated with specific circadian metabolic and physiological changes, and how the organization of sleep-wake states is related to regulation of nocturnal metabolism during fasting. Among the modifiable factors that can contribute to sleep-related benefits, emerging evidence suggests that diet and nocturnal changes in glucose regulation are strong determinants of sleep quality. Here, we review studies that have explored the importance of quantity and quality of dietary carbohydrates and proteins in modulation of sleep and sleep-related health benefits. Future research may guide the creation of nutritional solutions to improve sleep, which could lead to positive changes in health, wellbeing, and overall quality of life.

Physiological responses to carbohydrate overfeeding

PURPOSE OF REVIEW

To consider emerging research into the physiological effects of excessive dietary carbohydrate intake, with a particular focus on interactions with physical activity.

RECENT FINDINGS

A single episode of massive carbohydrate overload initiates physiological responses to stimulate additional peptide hormone secretion by the gut and the conversion of carbohydrate into lipid by the intestine, liver and adipose tissue. These acute responses maintain glycaemic control both via increased oxidation of carbohydrate (rather than lipid) and via nonoxidative disposal of surplus carbohydrate into endogenous glycogen and lipid storage depots. Sustained carbohydrate overfeeding therefore results in a chronic accumulation of lipid in the liver, skeletal muscle and adipose tissue, which can impair insulin sensitivity and cardiometabolic health in general. Beyond any direct effect of such lipid deposition on body mass/composition, there is not yet clear evidence of physiologically meaningful metabolic or behavioural adaptations to carbohydrate overfeeding in terms of other components of energy balance. However, regular physical exercise can mitigate the negative health effects of carbohydrate overfeeding, independent of any effect on the net carbohydrate surplus.

SUMMARY

Research in this area has advanced understanding regarding the mechanisms of weight gain and associated health outcomes within the modern context of an abundant supply of dietary carbohydrate.

Anti-diabetic effects of pomegranate extracts in long-term high fructose-fat fed rats

Background

A high-sugar or/and high-fat diets is a major risk factors for obesity. However, increased fruit and vegetable intake has been recently linked to obesity prevention. The aim of the present study was to investigate the preventive effects of pomegranate leaves (PL), juice (PJ) and peel (PP) extracts, on insulin resistance and oxidative stress in high fat and high fructose diet-induced obese rats.

Methods

Obesity in rats was induced by consumption of diet high in saturated fat and fructose (HFD) for a long period (12 weeks).

Results

Compared to the control group (CG) fed chow died, the high fat and high fructose diet (HFD) group showed a significant increase in the fasted plasma levels of glucose (29.8%), insulin (45%), amylase (70%) and lipase (54%). Moreover, HFD feeding has increased lipid peroxidation and protein carbonylation and decreased antioxidant enzymes levels. However, PL, PJ and PP treatment markedly prevents glucose intolerance, insulin resistance and oxidative stress and decrease amylase and lipase levels.

Conclusion

These findings highlight that a long-term intake of pomegranate extracts might be a potential alternative strategy for the prevention of a HFD induced insulin resistance and oxidative stress.

The biology of human overfeeding: A systematic review

This systematic review has examined more than 300 original papers dealing with the biology of overfeeding. Studies have varied from 1 day to 6 months. Overfeeding produced weight gain in adolescents, adult men and women and in older men. In longer term studies, there was a clear and highly significant relationship between energy ingested and weight gain and fat storage with limited individual differences. There is some evidence for a contribution of a genetic component to this response variability. The response to overfeeding was affected by the baseline state of the groups being compared: those with insulin resistance versus insulin sensitivity; those prone to obesity versus those resistant to obesity; and those with metabolically abnormal obesity versus those with metabolically normal obesity. Dietary components, such as total fat, polyunsaturated fat and carbohydrate influenced the patterns of adipose tissue distribution as did the history of low or normal birth weight. Overfeeding affected the endocrine system with increased circulating concentrations of insulin and triiodothyronine frequently present. Growth hormone, in contrast, was rapidly suppressed. Changes in plasma lipids were influenced by diet, exercise and the magnitude of weight gain. Adipose tissue and skeletal muscle morphology and metabolism are substantially altered by chronic overfeeding.