Fat cells remain with you for life: Short of procedures that remove fat from the body, such as liposuction, even a significant weight loss won't change the number of fat cells in your body. Weight loss results when you burn more calories than you take in. The body uses the fat for energy, making the fat cells shrink, nutritionist Katherine Zeratsky explains on MayoClinic.com.
Expert Insight
During weight loss, the body breaks down triglycerides into glycerol and fatty acids. The liver, kidneys and muscle tissue absorb the glycerol and fatty acids. Further metabolic processes break these substances down into energy for your body. The body's metabolic activities produce heat, which maintains body temperature. Waste products from metabolizing fat into energy in the body leave the body in urine, sweat and are exhaled from the lungs.
Significance
Understanding how the body works during weight loss can help you in choosing a weight loss strategy or in assisting others to lose weight. Even a moderate weight loss of 5 to 10 percent of your current weight can improve blood pressure, blood cholesterol, blood sugar -- and reduce the risk of chronic diseases, the Centers for Disease Control and Prevention reports. Diseases associated with obesity include heart disease, diabetes, hypertension -- high blood pressure -- certain cancers and a higher risk of disability, the CDC states.
Function
"Metabolism" refers to the body's process of creating energy. You metabolize foods and beverages to fuel your body's processes and physical activities. Your resting metabolism, or basal metabolic rate, includes basic bodily function. Everything from circulating your blood, regulating hormones, replenishing cells to breathing, requires energy. Your BMR uses 60 to 75 percent of your daily calories and processing food takes up about 10 percent more. The body uses the rest of your calorie intake for physical action and stores excess calories as fat. Physical activity is the area of calorie use that you can take active steps to control.
Effects
Weight loss accompanied by exercise makes the body more fit. Exercise, especially weight-bearing exercise, helps to maintain bone density, particularly important to post-menopausal women to help prevent osteoporosis. Strengthening the body through weight training and exercises that use the body's own weight such as push-ups, pull-ups, squats and lunges helps to maintain muscle.
During weight loss, many people lose lean tissue -- muscle mass -- in addition to fat. Strength training during weight loss helps to protect your muscle mass, which helps to counteract the slowing of your metabolism that occurs with aging or dietary restriction.
Considerations
Severely low calorie diets and fasting, especially if undertaken without medical supervision or for extended periods of time, can damage your health. An underfed body will use its own healthy cells to provide energy for survival.
When you expend more energy -- calories -- than you consume, your body burns fat for energy. Eating less and exercising more help to create the calorie deficit that lead to weight loss. For a safe and healthy rate of weight loss of 1 to 2 lb. a week, you need a 500- to 1,000-calorie deficit per day. A combined approach of consuming fewer calories and increasing exercise offers the best weight loss strategy, Nutrition.gov advises.
Consult your doctor about medical issues and weight loss concerns.
References
- MayoClinic.Com: When You Lose Weight, Where Does the Lost Body Fat Go?
- MayoClinic.Com: Metabolism and Weight Loss: How You Burn Calories
- Centers for Disease Control and Prevention: Metabolism and weight loss: How you burn calories
- Centers for Disease Control and Prevention: Obesity Among Adults in the United States
- Nutrition.gov: Weight Management FAQ
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