Do You Get Tired on a Calorie Deficit?

Weight loss occurs when you consume fewer calories than you burn. Reducing your daily caloric intake too much, however, can be counterproductive. You may be left with deficiencies in nutrition and energy, which may make you tired and affect your mood. A healthy weight-loss plan shouldn’t leave you feeling tired, but a quick weight-loss scheme might.

Fad diets and quick-weight-loss plans promise fast results, but they may reduce your calorie intake below healthy levels. Registered dietitian Joanne Larsen of the Ask the Dietitian website recommends you never dip below 1,200 calories per day even when trying to lose weight, because you will lose muscle if you consume fewer calories than that. Some fad diets, such as the grapefruit diet or the cabbage soup diet, may reduce your daily intake to as little as 800 calories per day. That does not provide your body the energy it needs to run effectively. When you consume fewer than 1,200 calories per day, it is difficult to get all the nutrients you need unless you are under a doctor’s supervision. Nutritional deficiencies, such as low iron, can also lead to extreme fatigue.

Diets that eliminate entire food groups can also make you tired. Some low-carb plans drastically reduce your intake of carbohydrates, which are the primary source of fuel for your body. "U.S. News and World Report" noted in 2011 that low-carb dieters, in particular, are more likely to feel tired than people who get 45 to 65 percent of their daily calories from carbohydrates, as recommended by the federal government.

If you simultaneously increase your physical activity while severely limiting calories, you may feel depleted. Oxygen Magazine cites a Penn State University study that reports that almost 50 percent of active women are undernourished and, as a result, experience hormone disruptions that affect fertility and bone health. These women are also unable to achieve their workout goals because of their limited caloric intake. You need energy for exercise. While you don’t want to negate the calories you burn with a large, indulgent meal, you do want a little fuel prior to exercise so you can have a productive workout. If you are exercising first thing in the morning or several hours after your last meal, eat a small 100- to 200-calorie snack an hour before you hit the treadmill or the weights so you have the energy to put forth your best effort and burn the most calories possible.

Instead of crash dieting and deprivation, implement healthy lifestyle changes that lead to long-term weight loss. Losing weight slowly is more sustainable, according to the American Heart Association. For a one-pound-per-week rate of weight loss, create a daily 500-calorie deficit by eating 250 calories fewer than you need to maintain your weight and exercising off an additional 250 calories daily. Limit your portion sizes, and choose healthy foods, such as whole grains, vegetables and lean protein. Skip desserts and soda and cut back on processed foods. Add at least 30 minutes of walking daily; if you can fit in more, you will likely experience better results. Moderate amounts of exercise and a healthier nutrition profile should boost energy, rather than reduce it.