The answer to that question is a definite NO!
Muscle and fat are two completely different and independent tissues in the body. If you were to stop strength training then of course the muscle you previously had will start to diminish. If you continue to eat the same amount of calories your as when you were training then the result will be that you gain fat. Strength training raises your metabolic rate so the more muscle you have the more calories you can eat without putting on fat. Once you have less lean muscle in your body your metabolism will naturally slow down, which means you have to eat less in order to stop yourself from putting on weight.
It is a similar principle to when one quits smoking. The caffeine in the cigarettes increases the metabolism, so when you don't smoke any more you have to increase your activity level in order to burn the same amount of calories so that you don't put on fat.
So the key point is – don't stop strength training! It is not only great for your health, but increases your metabolism and gives you a much nicer body shape than cardio alone! But if you have to stop, say due to injury, then make sure you adjust your calorie intake accordingly and use cardiovascular exercise to stay fit and healthy.
