Energy Balance Equation

Weight Loss and Body Composition

At our gyms in Cardiff we are constantly being asked about the best ways to lose weight and change body composition. Some people do it relatively easily making small adjustments to lifestyle and keeping a balanced diet whilst others struggle with weight control for years. One thing is certain, the human body functions in accord with the fundamental laws of thermodynamics, originating from the fields of mathematics, thermodynamics, physics and chemistry. The energy balance equation has been developed from those rules. The laws dictate that if total calories intake from food exceed daily energy expenditure then excess calories accumulate as fat in adipose tissue.

The Energy Balance Equation

The following diagram published in McArdle, Katch and Katch textbook Sport and Exercise Nutrition demonstrates the energy balance equation and how this relationship works.                         

 Energy Balance Equation Cardiff Gym


3,500 kcal = 1lb Body Fat.

The concept of energy balance most typically applies to body weight maintenance and weight loss. It is accepted in the scientific literature that a caloric deficit of 3500kcal gives a 0.45kg (1 pound) body fat loss. So if you divide 3,500calories by 7 days it means that by creating a 500kcal negative energy balance a day it will give a 0.45kg or 1 pound of body fat loss per week. This negative energy balance could be burning 500kcal more or eating 500kcal less. Alternatively you could burn 250kcal more and eat 250kcal less!

Consider the following kcal when choosing if you go for that extra snack in the coffee shop or add an extra glass of wine at dinner!


500ml Coke 210kcal

Starbucks Choc Muffin 484kcal

Choc Caramel Shortbread 499kcal

Starbucks Venti Latte 299kcal

Half a bottle of white wine 278kcal

Pint of Carlsberg 182kcal

58g Mars Bar 260kcal


Cardiff Personal Trainer and Sports Therapist