The yoyo effect is the loss of muscle (lean tissue) with each round of dieting. Muscle is metabolically active tissue; it is like a furnace that needs calories to exist. When you remove muscle you reduced the ability to burn calories at rest and during exercise. Every time body weight is reduced without preserving muscle tissue, through strength training, you must decrease the base caloric intake to avoid subsequent weight gain. If you increase your caloric intake and gain the weight you lost, you will have replaced the muscle loss with fat gain.  Strength training is the only way to minimize the loss of muscle tissue while reducing body weight. In fact, productive strength training while reducing caloric intake can reverse the drop in metabolic rate and increase muscle tissue. The increase of muscle tissue can ease the problem of weight control.  

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