I wish to lose weight and I am doing ok two stones in four months. I have cut my calorie intake knocked the beer and wine on the head and started cycling swimming and now joined a local gym. I am 62 so can't run now as it irritates my left knee and gives me back pain. Does any body know what goes first fat or muscle when I Exercise. Ultimately I would rather be heavier with a trimmer waistline no belly or man boobs than be really thinner but still flabby. One of the gym instructors says light repetitive exercise burns fat. One instructor says the body can turn muscle into energy easier than fat so will do this first. Articles say we burn fat and muscle at the same time.. Another says exercise involving weights builds muscle which then burns fat. Can anyone offer advice?