How long does it take for excess calories to turn into fat?

How long before excess calories start turning into fat?

Given the risks associated with excess body weight, it is very important to understand how body fat percentage starts to climb and how people become overweight. How long does it take? How does the body start storing fat, and how many surplus calories do you need to consume before fat storage kicks in?

Calories in fat

One pound of fat contains 4086 kcal, but because every fat cell also holds water, minerals and proteins, 1 pound (454 grams) actually provides about 3500 kcal.

Timing

Once a meal has been eaten, the body either uses the resulting energy right away or starts storing it in fat cells as body fat. Dr. David Katz tells “O, The Oprah Magazine” that the body starts storing excess calories as fat roughly 4-8 hours after you begin eating your last meal. The first 1000 kcal consumed are put into storage as glycogen in the liver and muscles. Our body works in such a way that once the glycogen calories are used up, it taps the calories stored in fat cells. Fat cells store calories in the form of triglycerides. Triglycerides are mobilized to meet immediate energy needs, but also to refill muscle and liver glycogen reserves.

Translator’s note: in other words, the first 1000 kcal are put into storage as glycogen in the muscles and liver, but once muscle and liver glycogen stores are full, the conversion of excess calories into body fat kicks in.

Aerobic training

Sustained aerobic physical activity stimulates the mobilization of stored fat from the body’s fat cells by increasing oxygen transport. According to researchers at the University of Georgia’s Department of Kinesiology and Health, aerobic activities are those that engage large muscle groups, raise the heart rate and last long enough. Such activities include jogging, jumping rope, swimming, cycling and others. The American Heart Association recommends that a healthy adult do at least 150 minutes of moderate-intensity aerobic activity per week. A training session should also last at least 10 minutes.

Translator’s note: clearly, “at least 10 minutes at a time” is a very modest recommendation; it should really be “at least 15-20 minutes at a time”. Some lighter strength training could be added to that. Going to a workout for ten minutes is neither sensible nor productive!

Strength training

While aerobic training directly burns energy from fat to meet the energy demands of the activity, strength training speeds up our metabolism and makes our body metabolically more expensive to run. According to the portal “Shape Fit”, 454g (each pound) of muscle burns about 30-50 extra kilocalories a day just to maintain itself. So the greater your muscle mass, the more calories your body burns at rest. The American College of Sports Medicine recommends focusing mainly on basic exercises in strength training and doing them at least twice a week on non-consecutive days.

Translator’s note: the main reason I translated this article was a wish to give at least an approximate answer to the question: how long does it take before excess calories start being stored as body fat? The answer is that it depends on how full our energy reserves are, including muscle and liver glycogen stores, and on what our energy expenditure has been and will be. Depending on the conditions above, fat storage begins 4-8 hours after the start of the last meal.

Author: Janar Rückenberg (translation)

Source: Turg.Fitness.ee

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