Nothing. It's an excellent starting point. But that's all it is- a starting point. Body composition is a much more meaningful indicator of health status than mere body weight.

If your basic objective is to be fit not fat, it's important you lose unwanted fat, not valuable muscle. Tracking your body composition helps you keep the proportions of muscle and fat within recommended limits. These have been established over many years and staying within the recommended ratios can produce significant health benefits. For example it can reduce the risk of premature heart attack. Fat weight -not total weight- determines health risk.

Historically the health professionals rely exclusively on the use of skinfold calipers to provide a better measurement then weight scales. Now the most popular and consistently accurate method is called "Bio - Impedance Analysis" or BIA for short.

Fat and muscle are known to produce different levels of resistance to electricity so BIA involves passing a safe signal through your body and measuring the resistance levels. The actual electronic measurement takes only 3 seconds.