Weight Loss by Limiting Calories

Topic Overview

Losing weight safely means balancing protein, fat, and carbohydrate with every meal and snack. You'll feel fuller longer as your body takes its time digesting the food. There is no perfect method for weight loss, but it helps to have a guide.

• Reduce calories from saturated fats to less than 10% of total calories by replacing them with unsaturated fats: monounsaturated and polyunsaturated.
• Choose complex carbohydrates, such as whole grains, vegetables, and fruits.
• Choose low-fat protein sources, such as fish, poultry, and legumes (for example, pinto beans, lentils, and split peas).
• Get enough fiber each day. Men should aim for 38 grams a day, and women should aim for 25 grams a day.
• Have no more than 1 alcohol drink a day for women and 2 alcohol drinks a day for men.

If you need some help making your meals and snacks balanced, a dietitian can help you create a plan that fits your lifestyle. Also, you can look at the nutrition facts label to figure out the fat, carbohydrate, and protein in foods.

Calories

In the tables below, find your gender, age, and activity level.

• Choose sedentary if your activity is limited to normal movement in everyday life.
• Choose moderately active if you do activity that is equivalent to walking 1.5 to 3 miles a day at 3 to 4 miles an hour.
• Choose active if you do activity that is more strenuous than walking 3 miles a day at 3 to 4 miles an hour.

*Pregnant or breast-feeding women have different calorie needs.

Very low-calorie diets

Use extreme caution with a very low-calorie diet (VLCD). You are starving your body. VLCDs generally are not recommended. Regaining weight is almost certain, which is damaging both physically and psychologically. If you need to lose weight, it is better to lose weight slowly. You will be more likely to lose the weight safely and keep it off.

Although initial weight loss is greater on a VLCD than on a low-calorie diet, in the long term about the same amount of weight is lost in both types of diets.^{footnote 2}

Diets this low in calories (less than 1,000 calories a day) generally do not provide enough nutrients for good health unless the diet is specially prepared. You will need the assistance of a health professional. A diet that does not have enough vitamins or minerals can lead to serious, potentially fatal health problems.

These diets are not recommended if you have heart problems, blood clotting problems, bleeding ulcers, liver disease, kidney disease, or cancer or if you have had a stroke. If you are older than 50, you will need frequent monitoring by your health professional to be sure you are losing fat and not muscle.

People on these diets often feel tired or have constipation, nausea, or diarrhea as a side effect.

The most common serious side effect is developing gallstones. People who are obese are more likely to develop gallstones than people who are lean, and when a person who is obese uses a very low-calorie diet, the chance that he or she will develop gallstones becomes even greater. People who lose a large amount of weight quickly are at greater risk than those who lose weight more slowly. But you can take medicine that helps prevent gallstones from forming.

The following are the changes your body goes through during a VLCD:

• Your metabolism slows to conserve energy because the body thinks it is starving. A slower metabolism burns fewer calories.
• To get the carbohydrate it needs, your body breaks down protein. You lose lean body tissues (muscle and organ tissue). It is important to preserve lean tissue, because it increases your basal metabolic rate. Losing too much lean tissue increases the percentage of fat in your body. The result is a reduced metabolism. This is one reason why it is so easy to regain weight after you lose weight quickly.
• In a VLCD (or during starvation), about half the weight you lose is fat and the other half is lean tissue, such as muscle. On a more moderate diet, you lose 3 times more fat than lean tissue. It is important to preserve lean tissue, since it increases your resting metabolic rate.
• Mineral and electrolyte imbalances can occur. These imbalances can be life-threatening. This is the reason these VLCDs must only be used under a health professional's supervision.
• Bone mass is lost. This is more risky for women, because they diet more often than men, and they are also at higher risk for osteoporosis.