Go ahead and indulge your cravings. Take a break from working out. But return to your normal diet and exercise program the next morning. A review in the British Journal of Sports Medicine found that the longer it takes you to re-focus on fitness, the more your enthusiasm for it will dim, and the harder it will be for you to get back on track. In short, a day off won’t hurt you, but a week or two off can derail your progress toward your goals. It can also inflate your waist size, according to a study in the Journal of Applied Physiology. The researchers found that just two weeks of inactivity can increase belly fat by seven percent.