How Fast Can I Lose Weight Just by Cutting Calories?

Cutting calories is a reliable way to lose weight, with or without exercise. However, it can be difficult to stick to a low-calorie diet for an extended period of time, which is why many people choose to burn additional calories through exercise. If you diet without exercise, you will need to eat the right foods and accept that your weight loss will include more muscle loss than if you worked out to lose weight.

A woman is using a measuring tape. (Image: mrcmos/iStock/Getty Images)

Factors That Determine Weight Loss

You need to burn 3,500 more calories than you take in to lose 1 lb. How many calories you burn each day beyond what you consume depends on a number of factors. Your body will use more calories if you are heavy than if you are light. Males burn more calories each day than females. You use more calories if you work in carpentry than if you work at a desk. To predict how many calories your body will use each day, use an online basal metabolic rate calculator. This tool will give you the number of calories that you need for basic survival. Cut calories from that number to lose weight.

Sample Prediction

A 20-year-old woman who weighs 180 lbs. has a basal metabolic rate, or BMR, of 1,650 calories. If she goes on a 1,200 calorie diet and leads a sedentary lifestyle, she is likely to lose approximately 1 pound per week. Meanwhile, she is not building calorie-busting muscle, since she is not exercising. Some of the weight she loses is likely to come from existing muscle as well at fat cells. This scenario can be discouraging, for while she may lose 4 pounds of weight in a month, if she regains it later, she may end up being even larger, as she will have gained 4 pounds of fat, when the original weight that she lost was both fat and muscle. For this reason, it is a good idea to lose weight in a manner that you believe you can sustain for the long run.

Activity Level

One factor that determines how fast you can lose weight is your overall activity level. If you are sedentary, you will find it difficult, although not impossible, to lose weight solely by cutting calories. Long-term weight-loss success is more likely if you exercise. Individuals who have kept their excess weight off for over 5 years typically exercise for 1 hour each day, according to the National Weight Control Registry. By exercising, you can burn an extra 300 to 800 calories a day, depending on the intensity of the activity and your weight. If you choose not to exercise, you will lose weight more slowly. If the woman in the example above burned 500 calories each day exercising, she would likely lose 2 pounds per week instead of only 1 pound.


You may find it easier to stick to a low-calorie diet if you include plenty of protein, which provides more satiety than carbohydrates or fat. A 2005 study published in the "American Journal of Clinical Nutrition" found that people who got 35 percent of their calories from protein, 20 percent from fat and the remainder from carbohydrates ate fewer overall calories each day and reported less hunger. Also include a variety of colorful vegetables and fruits to keep your nutrient intake — and your energy level — high.

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