"There is no magic pill or food that can boost your metabolism," Kim Rose, RDN, told POPSUGAR. "An increased metabolism is only associated with weight loss or weight maintenance. The more lean muscle you have, the higher your metabolism will be, and the older you are, the lower your metabolism will be." Eating hot peppers or drinking lemon water first thing in the morning won't do it, but if you want to improve your calorie burn, these healthy habits — including strength training — can help.