Which is the best strategy for avoiding chronic diseases caused by a high-calorie diet?

The correct answer is C. A. would require a drastic sudden change which would only damage the body as it wouldn't be immediately used to it, as well as it wouldn't gain enough nutrients from which to gather energy for exercising; B. is an unhealthily wrong choice, because exercise is efficient, but diet influences at least 80% of the weight results; C. is the most balanced choice.