Does losing weight decrease cancer in older women?
During weight reduction, there is a decrease in circulating estrogen and other sex hormones that would be expected to promote osteoclastic activity directly or indirectly due to increased levels of cytokines (i.e., IL-1, IL-6, tumor necrosis factor-α). In addition, there was a rise in the Ca-PTH axis during energy restriction in women consuming low/normal Ca (0.6–1.0 g/d), but not in those whose Ca intake was high (1.7 g/d); this could contribute to a rise in bone resorption. Although vitamin D intake is typically reduced () during moderate energy restriction, reduced serum levels were not observed. The adipocyte-derived hormones leptin and adiponectin may also play a role in bone metabolism during weight reduction. The anorexic effect of leptin is not apparent in obesity due to leptin resistance, whereas levels decrease with weight loss. The central effects of leptin inhibit bone formation (), whereas leptin has direct effects on osteoblasts () and indirectly affects osteoclasts (), possibly through sympathetic signaling (). The relation between leptin and bone during weight reduction is likely dependent on a number of factors such as obesity, gender, age, ethnicity, and leptin resistance (). Adiponectin is typically low in obesity and may increase with moderate weight loss (). Because adiponectin suppresses osteoclast number and activates osteoblastogenesis (), it is possible that a rise due to weight reduction would have a beneficial effect on bone mass. In addition, the gut-derived hormone, ghrelin, also increases with weight loss (to stimulate appetite) and stimulates osteoblastic proliferation and differentiation (). However, severe weight loss due to gastric by-pass surgery decreases serum ghrelin levels to almost undetectable levels (), which could have a detrimental effect on bone. Another gastrointestinal hormone, glucagon-like peptide-2 (GLP-2) increases bone mineralization and reduces bone resorption, yet decreases due to weight reduction (). Serum IGF-I is suppressed during energy or protein restriction, and the anabolic effect of IGF-I on bone is well established (). Finally, serum cortisol may increase with acute fasting () or moderate weight loss (), especially in low estrogen states () to increase osteoclast activity and/or decrease Ca absorption (). Overall, weight reduction decreases serum estrogen, leptin, GLP-2, growth hormone, and IGF-I and/or will increase cortisol; these changes would be expected to have a detrimental effect on bone mass. However, the rise in adiponectin and ghrelin with moderate weight loss may prevent excessive loss of bone. The balance of hormonal changes during weight loss and their effect on bone depend on other factors such as age, gender and/or amount and type of weight loss.
Naturally losing weight is a healthy and safe method of weight loss
Does body weight affect cancer risk?
Fatigue toward the end of a prolonged sporting event may result as much from dehydration as from fuel substrate depletion. Exercise performance is impaired when an individual is dehydrated by as little as 2% of body weight. Losses in excess of 5% of body weight can decrease the capacity for work by about 30% (Armstrong et al. 1985; Craig and Cummings 1966; Maughan 1991; Sawka and Pandolf 1990).
Weight Management and Blood Pressure