Last minute summer shape-ups could do more harm than good. That´s according to the San Diego-based American Council on Exercise. Fitness professionals say jumping into a diet or exercise program could result in injury and won´t be well-received by your body. The best way to shape up for summer, they say, is to start exercising slowly and build to three work-outs per week. They say that should include strength training, which will help you burn fat. The council also says you should avoid fad diets and, instead, reduce your portion sizes.