1. Lack of sleep

Why: “When you’re tired, your levels of the leptin hormone drop, and your appetite increases,” explains Dr. Oz.

What to do about it: “If you can’t get a full 8 hours a night for a few nights in a row, don’t stress,” he says. Melatonin supplements may help.

2. Your diet

Why: If you’re already eating a low-calorie, low-fat diet and your weight is still creeping up, or you can’t shake that fatigue, Dr. Oz says to take a closer look at your food intake, especially the amount of sugar in your diet. “Sugar affects insulin levels,” he explains. “High insulin leads to sugar cravings, which can wreak havoc on your metabolism.”

What to do about it: “Cut down on the amount of sugar in your diet, especially the sugary beverages,” he says. “If you can’t cut them out completely, substitute with seltzer and a splash of fruit juice — that way, you get the taste and feel of a sugary beverage, but it won’t kill your blood sugar levels.” While you’re at it, watch out for high-fructose corn syrup lurking in packaged foods. Swap unprocessed snacks for processed ones — i.e., pretzels instead of potato chips or crackers — whenever possible and don’t buy products labeled “reduced sugar” or “sugar-free.” They often contain artificial sweeteners that can actually be worse for your waistline than real sugar.

3. Stress

How: When you’re stressed, you produce high levels of the cortisol hormone, which triggers the body to store fat in the abdominal area. “When you’re chronically stressed, you also tend to eat more because of the effects of cortisol on blood sugar levels,” Dr. Oz says.

What to do about it: Yoga and meditation can help relieve stress by lowering cortisol levels, improving sleep quality, and increasing your energy level. “You’ll find that not only will your body shapeshift, but you’ll also feel more relaxed and at peace, which will help you make better food choices,” says Dr. Oz.

4. Your genes

Why: “You may not be able to control your parents’ weight, but you may still be stuck with their fat-storing genotype — especially if both of them tend to carry extra pounds around the middle,” says Dr. Oz.

What to do about it: “It’s not your fault,” he says. Still, with a little extra effort and some gene-specific suggestions from the doctor, you can turn things around for good.

5. Not enough protein

How: “You may be eating less than you think when it comes to protein — especially if you’re loading up on carbs,” says Dr. Oz. “When you eat refined carbohydrates like bread or pasta, your body deals with them almost immediately, so it’s easy to think you don’t need much protein,” he explains.

What to do about it: “If you want to lose weight and trim your middle, aim for 10% of your daily calories to come from protein,” says Dr. Oz. “To figure this out, just divide your weight in half and eat that many grams of lean protein per day.”