How Long Does It Take to Lose Body Fat?

Lose Body Fat
Lose Body Fat

Use Science to Lose Body Fat

Losing body fat can pose a challenge. People who attempt to shed it often feel discouraged due to its stubborn nature. However, learning some facts about human physiology, specifically how the body stores and burns body fat, can be helpful. These facts reveal some remarkable insights that can assist people in losing body fat.

A Few Facts About Fat and Our Bodies

One fact about nutrition is that burning one pound of fat requires approximately 3,500 calories. Scientists measure this by burning one pound of fat and gauging the produced heat (1).

A second fact about the human body is that fat is like the storage of excess calories. Caloric Balance is a simple formula of total calories in minus total calories out. If our caloric balance is positive, we have excess calories that the body converts into stored fat. Conversely, if our caloric balance is negative the body will begin to burn stored fat.

Another fact is that people with higher muscle mass and lower body fat burn calories at a higher rate. Therefore, doing strength training to increase muscle mass can assist people who want to achieve losing body fat loss. When strength training is combined with cardiovascular activities like jogging, the results can be even better.

The Mathematics of Weight Change

The mathematics of weight and fat change uses these and other facts. Expected weight or fat change in pounds is equal to caloric balance divided by 3,500 calories. Calories consumed are the sum of calories from food and drink. You burn calories based on your baseline metabolism, also known as your basal metabolic rate. You also burn calories based on your non-sedentary activities like exercise, work, and household chores.  If caloric balance, again, the difference between calories in and out, is:

  • Positive – we should expect weight and fat gain.
  • Zero – we should expect no weight and fat change.
  • Negative – we should expect weight and fat loss.

The Pace of Burning Fat

How slowly or quickly a person loses body fat depends on their caloric balance. Adult males burn about 2,500 calories per day and adult women burn about 2,000 calories per day. If a man or woman fasts for a day, then their caloric balance would be -2,500 and 2,000 respectively. Therefore, dividing by 3,500 calories equates to the man and woman losing 0.7 and 0.6 pounds of body fat, respectively. However, complete fasting is not a long-term viable option for losing body fat because the body needs nutrition. Perhaps a more reasonable goal is to lose a pound of fat per week. This goal requires a negative caloric balance of 500 calories per day. Eating a smaller meal or cutting out an afternoon snack can achieve this calorie reduction.

Footnotes
1. Food calorimetry allows us to determine the number of calories per gram of food. We place a sample of the food in an insulated, oxygen-filled chamber surrounded by a specific amount of water. This device is called a a bomb calorimeter. Then, we burn the sample completely. The heat from the burning raises the temperature of the water. We use the temperature change of the water to determine the amount of energy in the food.

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