Burning off fat

OVERWEIGHT and obesity are increasing at an alarming rate across the world.

Obesity represents a serious health risk, as it increases the risk of diabetes, hypertension, heart disease, and cancer. The close association between obesity and diabetes has given rise to the term “diabesity”.

Obesity can occur when an individual is in positive energy balance, which is the scientific way of saying they eat more calories (energy) than they use. This may be shown by the following equation: Energy balance = energy intake – energy expenditure.

When the calories (energy) eaten are greater than the calories (energy) used, the energy balance is positive and the energy not used is stored as fat. A chronically positive energy balance can therefore lead to obesity.

In contrast, to achieve weight loss, an individual has to be in negative energy balance. This can be achieved by either reducing food intake or increasing energy expenditure.

For several decades, the conventional strategy for weight loss has been the recommendation to reduce food intake (calorie intake). Such programmes based on food restrictions have been of limited long-term success due to the dramatic fall in basal metabolic rate (BMR) when food intake is restricted.

The largest contributor to energy expenditure is BMR, which may be defined as the minimal rate of energy expenditure required by your body to sustain life.

So if your BMR falls as a result of eating less food, then even though you are taking in less energy, you are also using less energy, so other factors need to be considered to reach the goal of weight loss.

Your body also burns energy when you exercise, and for younger people and pregnant women, for growth. This article takes a look at a fourth way that your body uses energy, namely by eating certain foods, known as thermogenic foods, that cause an increase in BMR and cause your body to use more energy.

BMR represents approximately 605 to 75% of total energy expenditure (TEE) in adults, and is influenced by gender, body size, body composition, and age.

Total energy expenditure (TEE) is composed of: BMR, physical activity (PA), dietary induced thermogenesis (DIT) or Thermic effect of food (TEF), and growth (G). In non-pregnant, non-lactating adults, growth makes little or no contribution to energy expenditure, and therefore, TEE = BMR + DIT + PA

DIT is sometimes referred to as the thermic effect of food (TEF) and is an important component of energy expenditure after physical activity. The percentage increase in energy expenditure over BMR due to DIT ranges from 8% to 15% depending on the composition of the food consumed.

Between protein, fats, and carbohydrates in foods, it is recognised that a high protein diet elicits the greatest DIT (up to 15%).