Weight loss

Health

Fat accumulation in the liver (not related to alcohol, viral infection or liver diseases) is associated with obesity, insulin resistance, diabetes and alteration of lipid profiles, oxidative stress, mitochondrial dysfunction and inflammation.[1] Weight loss significantly improves fasting flow-mediated vasodilation of the brachial artery in adults (a measurement of endothelial function).[2] A meta-analysis of 20 studies involving 1259 participants indicated that weightloss (mean 8% of initial bodyweight) improves pulse wave velocity (a measure of arterial stiffness).[3]

Though exercise increases insulin sensitivity (preventing insulin resistance)[4], calorie restriction does the same, through autophagy.[5][6] This is regardless of whether this restricted diet is moderate-carbohydrate (40-45% of energy) and increased-protein (25-30%), or high-carbohydrate diet (55-60%) and moderate-protein (15%).[7] A low-calorie diet significantly improves the HRR (Heart Rate Recovery) after maximum exercise, predicting cardiovascular disease risk and mortality.[8] Menstrual disturbances are associated with energy deficits over 470 kcal / day.[9]

Gender

A systematic review of 49 high-quality scientific studies shows that there is little evidence to indicate that men and women should adopt different weight loss strategies.[10]

Nursing

Intensive nursing strategies for increasing self-efficacy for weight control and health-promoting behaviour may be essential components for better weight loss in the initial stage of a weight management intervention. Particularly increases in diet self-efficacy had a significant indirect effect on initial weight loss.[11] Individuals vary in their responsivity to cues that motivate overeating. Those higher in responsivity need specialized self-regulatory skills. These skills include an ability to tolerate uncomfortable internal reactions to triggers and a reduction of pleasure, behavioral commitment to clearly-defined values, and metacognitive awareness of decision-making processes. Such acceptance-based interventions based on these skills have so far proven efficacious for weight control, especially for those who are the most susceptible to eating in response to internal and external cues.[12] Subjects that readily loose most weight, have higher responsive fatty acid levels, and lower changes in leptin and insulin concentrations, suggesting a better metabolic flexibility. To reduce compensatory responses one needs to account for individual activity level before prescribing weight-loss program associating diet and exercise.[13] Step counts (10.000/day[14]) may be a key area to target.[15] Problem solving is another key component.[16] Successfully achieving the target weight loss in a comprehensive program predicts subsequent maintenance of lower weight without increasing the risk of dropout.[17] Providing the additional strategies at predetermined times over the intervention period enhances weight loss.[18]

Hormones

Constitutional thinness is associated with high PYY (peptide tyrosine tyrosine; secreted by intestinal cells[19]) in circadian profile.[20] Ghrelin and PYY are both involved in short-term regulation, while leptin is a long-term regulator of energy balance. Ghrelin (stimulating appetite) is similarly suppressed by lipid and protein, but duodenal lipid more profoundly stimulates plasma PYY as compared to the effects of protein on PYY. Neither intraduodenal lipid nor protein affects plasma leptin.[21] Protein increases PYY more than maltodextrin (absorbed as glucose).[22] Meat stimulates PYY and suppresses ghrelin more so than a vegan meal does.[23] Slow spaced eating does not affect PYY and ghrelin levels.[24][25]

Polydextrose (a water-soluble fiber) does not affect Ghrelin or PYY.[26] Cellulose (10% w/w; water-insoluble) also does not, but the water-soluble fibers beta-glucan (in cereals and bran), and particularly fructo-oligosaccharide and pectin (both present in fruits and vegetables) (all 10% w/w) increase PYY levels 2.3-, 3.1- and 3.0-fold respectively, and decrease bodyfat. A 5% dietary fiber content is insufficient to elicit these effects.[27] On the other hand, fiber is not included in caloric value, but fiber in general may contribute to weight gain through improved energy extraction from diet by the conversion of dietary fibre to short-chain fatty acids, such as propionic acid and acetic acid, substrates for de novo lipogenesis and gluconeogenesis.[28]

Calorie restriction

Adherence to any diet may result in weight loss, regardless of whether low in carbohydrates or low in fat.[29] The analysis of 119 scientific publications in participation with ten medical specialty societies resulted in the recommendation that for the purpose of weightloss and stabilization of a lower weight, a diet with an energy deficit of 500 kcal/day and a low energy density should be instituted.[30] Alternate-day fasting (25% energy intake alternated with ad libitum) diet decreases body weight, BMI and fat mass, regardless of whether the diet is high (40%) or moderately low in fat (25%).[31] Negative-calorie diets ("containing less energy than required for its digestion") and low-calorie diets are equally efficacious regarding weightloss.[32] Very-low-energy diets and ketogenic low-carbohydrate diets are associated with a suppression of appetite, despite weightloss.[33]

Weightloss and Exercise

Endurance training per se increases peak fat oxidation during exercise.[34] Combining caffeine with exercise creates a greater acute energy deficit. Caffeine also leads to exercise being perceived as less difficult and more enjoyable.[35]

Aerobic exercise training in women typically results in minimal fat loss / reductions in bodyweight.[36] Exercise interventions (55-64%) more than than diet interventions (12-44%) tend to trigger behavioral compensation (resulting in less weight loss).[37] 75% of subjects self-report to engage in compensatory eating in response to exercise, for reward, relief and recovery.[38] Meta-analyses of 45 scientific trials involving 7788 individuals revealed that interventions that deal with both diet and physical activity show small benefits on weight loss.[39] A quantitative analysis of 21 scientific trials (including 3521 participants), revealed that comparing exercise versus diet, diet resulted in a significantly more pronounced decrease in body weight. Diet plus exercise, in comparison to diet alone, reduced total fat, but did not result in a reduction in waist circumference. [40] As compared to diet restriction alone (energy content based on 70% of measured resting metabolic rate), the addition of strength or aerobic training does not improve changes in BMI, body fat or metabolic risk factors.[41] Dietary restriction with and without exercise result in similar weight loss and no signficant changes in the resting metabolic rate.[42] If not followed up by exercise, low-calorie-induced weight loss will result in a decrease in total energy expenditure and non-training physical activity energy expenditure. (less weight to carry around) Resting energy expenditure will decrease regardless of whether weight loss is follwed up by aerobic or resistance exercise, or not. [43] The latter may be due to an increase in autophagy. Low physical activity protects lean body mass.[44] Performing aerobic exercise after an overnight fast does not accelerate the loss of body fat, compared to non-fasted exerrcise.[45]

Compared to food restriction alone, the addition of running wheel activity makes mice loose weight faster, but also prevents further weight loss beyond a crucial point of body weight loss (especially fat mass). Both restricted groups adapted their energy metabolism differentially in the short and long term, with less fat oxidation and a preferential use of glucose in the mice that were also submitted to running wheel activity.[46]

Yoga

High intensity exercise stimulates compensatory eating. Bikram yoga meets requirements for exercise of light-to-moderate intensity and, theoretically, could be used for weight maintenance or weight loss if practiced several times per week.[47]