Question

Explain briefly how hydration levels affect skinfold, BIA and DXA measurements.

Answer 1

Skinfold measurement requires measuring the skin folds at different places with the use of callipers that help determine the body fat percentage. When the body content of water decreases it results in moving of wter from the slin into the tissues decreasing the skin fold thickness. Similarly when the body is overloaded with water, the tissue fluid is expelled out into the skin resulting in greater thickness of skinfold.

Body impedence measurement or BIA is the measure of electrical impedence contained by a body cell due its water or fluid content.
When body tissue contains more percentage of fat it will have a greater impedence while a body tissue with less fat content will easily allow to electrical current to pass through it and have a lower impedence. This is because water content in fatty tissue is lesser compared to other tissues.
DXA or dual-energy X-ray absorptiometry helps determine the body fat percentage through use of xray beam absorbed by the body tissues. When xray radiations pass through the body, bone have the least amount if water content and absorbs the most amount of xray and appear white. Fat tissue and air as they have least amount of water content absorb least amount of X-rays and appear black. Other body tissues such as muscle and lean body mass absorb Xrays higher than fat and appear grey.
So we saw that content of water affects the body fat percentage in body measures through different techniques such as BIA, DCA and skinfold. The basis of these tests is that fat tissue contains less amount of water as compared to other tissues such as muscles.