Effects of diets and their role in weight control.
ABSTRACT This study examines the secondary effects of hypocaloric diets. The results show that the positive short-term effects with regards health are not maintained in the long term, as most people eventually return to their original weight. A description is given of how psychological reasons are more important than biological mechanisms when explaining this failure and stress is put on how carrying out successive hypocaloric diets can result in a subgroup of people becoming overweight or obese. Furthermore, an analysis is made of the relationship between diets, eating disorders and the "yo-yo effect", which is in turn associated with a rise in morbimortality due to a wide range of causes. As an alternative to the indiscriminate use of hypocaloric diets, a strategy based on the modification of lifestyle is suggested in order to control weight and improve health.
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ABSTRACT: The intake of food and the expenditure of calories is modelled by a system of differential equations. The state variables are the amount of calories stored in adipose tissue and the level of plasma leptin. The model has as input a drive that controls the intake of food. This drive consists of a collective of physiological and psychological incentives to eat or to stop eating. An individual based approach is presented by which the parameters of the system can be set using data of a subject. The method of analysis is fully worked out using weight data of two persons. The model is prone to extensions by transferring incentives being part of the input to the collection of state variables.PLoS ONE 09/2013; 8(9):e74997. DOI:10.1371/journal.pone.0074997 · 3.53 Impact Factor
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ABSTRACT: Recent data suggest that chronic low-grade inflammation, a characteristic of obesity, is associated with altered tryptophan (Trp) and tyrosine (Tyr) metabolism and plays a role in neuropsychiatric symptoms. The present study assessed the effect of an extreme short-term diet on Trp breakdown and inflammatory biomarkers in overweight adults. Thirty-eight overweight participants (16 women, 22 men; average body mass index: 29 kg/m(2), mean age 52.8 years) were randomized into two diet groups: a very low kcal diet group (VLCD; Ø 600 kcal/day, n = 21) and a low kcal diet group (LCD; Ø 1,200 kcal/day, n = 17). Assays included the measurement of Trp, kynurenine (Kyn), and their ratio, neopterin, phenylalanine (Phe), Tyr, as biologic markers; leptin, plasma insulin, glucose, and homeostatic model assessment-insulin resistance; and interleukin 6, tumor necrosis factor alpha, and C-reactive protein, as biochemical and inflammatory markers at baseline and after 2 weeks of treatment. Weight loss diet lowered leptin levels in both groups by 46 %, although not reaching significance. Trp and Kyn decreased significantly by 21 and 16 % for VLCD and by 15 and 17 % for the LCD group, respectively. A significant reduction in Phe was only seen after VLCD. Inflammatory biomarkers, neopterin, and Tyr were not significantly altered during the study period. Leptin was significantly correlated with Trp breakdown before and after the intervention (P < 0.02). Since disturbed metabolism of Trp affects biosynthesis of serotonin and might be associated with increased susceptibility for mood disturbances and carbohydrate craving, strategies to supplement Trp while dieting could be highly useful in treating uncontrolled weight gain or in preventing neuropsychiatric symptoms.European Journal of Nutrition 04/2014; 54(1). DOI:10.1007/s00394-014-0690-3 · 3.84 Impact Factor
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ABSTRACT: Background: Dieters often show weight cycling, i.e. prior successful weight loss is followed by weight gain. The current study examined how goal progress during a diet (i.e. weight loss) impacts subsequent weight loss depending on whether success is identified on the process level or the outcome level of dieting. Methods: A short-term longitudinal study examined lagged effects of weight loss and identifications of success in one week on weight loss in the subsequent week. Across 6 weeks, N = 126 overweight women reported their weekly weight and the degree to which they considered themselves as successful regarding the process of dieting (e.g. changing eating behavior) and the desired dieting outcomes (e.g. improving appearance). Results: Successful weight loss in one week negatively affected weight loss in the subsequent week. However, identifying success on the process level reduced this negative effect. Discussion: Although people might feel generally that goal progress licenses subsequent goal-inconsistent behavior, identifying successful goal-pursuit on the process rather than the outcome level of a goal may counteract the subsequent loss of dieting motivation.Applied Psychology Health and Well-Being 11/2013; DOI:10.1111/aphw.12021 · 1.75 Impact Factor