Effects of Weight Loss and Weight-Bearing Exercise on Blood and Organ Concentrations of Lead and Some Essential Metals

Thousands of years of human evolution have resulted in the selection of genes that enhance the ability to survive during extended periods of starvation or reduced energy intake. However, this has occurred in the absence of extensive exposure to environmental pollutants. Adults cur-rently living in industrialized countries have body lead burdens about 500 times greater than those who lived prior to widespread lead dissemination in the environment. Most (>95%) of the lead burden is stored in the skeleton. During rapid weight loss, there is a decline in bone mass in addition to soft tissue mass. This bone mass loss may mobilize skeletal lead. However, weight-bearing exercise during weight loss may prevent or reduce bone lead mobilization and redistribu-tion to other organs. The objective was to determine the effects of weight loss, with and without weight-bearing exercise, on lead and essential metal stores in rats with prior lead exposure. Fifty-five, 12-week-old, female, Sprague-Dawley rats were exposed to 400 ppm lead as the acetate in drinking water for 4 weeks, followed by a one-week period without lead exposure. The rats were randomly assigned to seven groups before the start of food restriction. The seven groups were weight maintenance (WM) with ad lib feeding, moderate weight loss (MWL) with 25% food restriction and substantial weight loss (SWL) with 50% food restriction, with or without treadmill running, and one background group euthanized before food restriction. Tread-mill running speed was gradually increased to