A while ago there was some discussion on if the body adjusts metabolism after weight loss to maintain the higher weight. Here's an article that talks about the issue: Why lost weight returns after dieting http://www.news-medical.net/?id=2955 The data suggests that weight loss in obese, obesity-prone rats, induced by caloric restriction, is accompanied by metabolic adaptations that predispose one to regain the lost weight. In rats that are losing weight, this is exhibited by a significant reduction in metabolic rate, measured as both 24-hour energy expenditure and sleeping metabolic rate, both independent of metabolic mass and energy intake. This adaptation persists after eight weeks of intake-regulated weight maintenance, but is no longer present with eight subsequent weeks of feeding at-will where rats are regaining lost weight. While rats that are regaining weight may have a shift in appetite that would contribute to their high rate of weight regain, the drive to increase food intake remains the most critical factor in the predisposition to regain lost weight. This adjustment clearly weighs more on the energy balance equation than the metabolic adjustment on energy expenditure observed in this or any other study. Additionally, the effect that energy intake, or more particularly, carbohydrate intake, has on respiratory quotient [dividing the amount of CO2 produced (VCO2) by the amount of oxygen uptake (VO2)]. RQ is much more dramatic than the metabolic adjustment observed from weight reduction. This drive to increase food intake likely involves environmental stimuli (diet composition, food palatability, physical activity) influencing motivational and metabolic components of a genetically determined set of central systems. While the data suggest that these metabolic adaptations might hinder successful weight maintenance, it should not imply that successful weight maintenance is unachievable. Even with the increased intake of carbohydrates, regular physical exercise may be the key factor that counteracts these metabolic adaptations to weight loss. ---- I notice that after everyone of these pronouncements saying how hard weight is to lose they say something like it's not unachievable. How hard does something have to be before people stop trying to achieve it? Not very hard.