Commercial diets and weight-loss products often make unrealistic claims for the rate of fat loss. Extreme diet and weight-loss supplements can cause you to lose water, sugar stores and muscle instead of fat. Though the value will vary depending on your weight, 1 to 2 lbs. of fat--approximately 0.3 to 0.5 percent body fat--can be safely and sustainably lost per week.
Fat Loss, Not Just Weight Loss
Promotions for diets and weight-loss products often use weight loss and fat loss interchangeably, although they are distinct processes in the body. For example, much of the weight loss during the first few weeks of a low-carb diet is glycogen--sugar stores--and body water. In a very low-calorie diet, glycogen, water and muscle are lost until your body slows your metabolism.
How to Lose Fat
The biological role of fat is to store energy for a time when ample food is not available to sustain your energy expenditure. Your body regulates energy intake through appetite, energy storage by stimulating fat use or storage, and energy expenditure by regulating physical activity. Any great change in these causes defense mechanisms to kick in and your metabolism to slow. The best way to lose fat is by a modest but long-term decrease in energy intake and increase in energy expenditure.
Calories and Fat
Each pound of body fat can produce 3,500 calories of energy. A caloric deficit from diet and exercise of 500 calories per day would allow you to lose 1 lb. a week. John Berardi Ph.D., founder of Precision Nutrition, has found that both men and women can reliably and safely lose 0.678 percent of their body weight on average per week. Although many factors regulate the burning of body fat, the bottom line is that calories in must be less than calories out. It is also important to note that obese adults should not lose more than 1.5 kg or 3.3 lbs., to prevent the risk of gallstones.
Measuring Your Progress
Your absolute weight can vary depending on hydration, undigested food, waste and other factors. You can roughly measure body fat loss by calculating your body mass index, or BMI. More accurate measure can include taking body measurements or having a fitness professional measure your body fat level using a skinfold test.
References
- Precision Nutrition: The PN Weight Loss Calculator Updated; John M Berardi; February 2011
- "American Journal of Medicine"; Medically Safe Rate of Weight Loss for the Treatment of Obesity: A Guideline Based on Risk of Gallstone Formation; R.L. Weinsier, et al.; 1995
- FamilyDoctor.org: What It Takes to Lose Weight; December 2010
- MayoClinic.com: Getting Past a Weight-Loss Plateau
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