# Metabolic Myths

#### Predictive equations accurately estimate energy expenditure

There have been numerous mathematical equations (Benedict - Harris, Schofield) developed to estimate resting energy expenditure using simple parameters such as height, weight, age and gender.

Many scientific studies have reported a significant error when using these predictive equations in comparison with the gold standard indirect calorimetry measurements.

It is common for predictive equations to significantly over-estimate resting energy expenditure. This has consequences for all health practitioners that use equations to prescribe calorie-controlled eating plans for their patients.

#### Overweight and obese people have slow metabolic rates

There is a positive correlation between metabolism and body surface area. That is, the larger the body surface area, the higher the metabolic rate.

This correlation would suggest that an overweight or obese person is more likely to have a higher metabolic rate than normal, and this is frequently shown to be true.

#### Energy levels are measured with a blood test

There is only one accurate method to measure human energy expenditure and this involves the use of calorimetry. This involves a breathing test at rest to monitor a patient's respiratory gases.

#### Athletes have a faster metabolism than the sedentary population

Your resting metabolic rate is controlled by a number of hormones released from different glands in the body (thyroid, adrenal and pancreas). Further, there is a direct correlation between body surface area and metabolism. Athletes are generally lean with a lower body surface area than an overweight person. Further, some athletes can be deficient in the hormones that stimulate energy production due to over-training. Therefore, athletes do not always have a faster resting metabolism than the sedentary population.

#### Glucose is the most important fuel for metabolism

The human body has evolved over many thousands of years to produce a highly efficient energy system. This energy system relies on three different fuels; glucose, fat and protein.

Each of these fuels has a different role in the manufacture and supply of energy which may vary depending on the organ or the body's demand for energy.

For example, the human brain relies completely on glucose for all of its energy requirements and is not able to use either fat or protein as a fuel source; however it can use ketones - a byproduct of fat metabolism. Further, human muscle also relies on glucose for energy during very high intensity physical activity.

#### However, the fuel that is most used to manufacture energy is fat. There are a number of fundamental reasons why fat is more important than glucose including;

a. More calories of energy (9.0) can be manufactured from 1 gram of fat compared to 1 gram of glucose (4.0).

b. Up to 80% of all energy is manufactured from fat stores during sedentary activities.

c. The body is able to store a near unlimited supply of fat however the storage of glucose is very limited. In fact, any surplus glucose that cannot be stored in the liver or muscle is converted to and stored as fat.

#### Energy diseases are well diagnosed and treated

It has been established in some countries that patients presenting with energy disorders and symptoms account for one third of all medical consultations.

The successful treatment of any medical condition is generally reliant on an accurate diagnosis performed by the Practitioner. In the treatment of energy disorders however, the energy production process (metabolism) is very rarely assessed using the correct procedure (indirect calorimetry) and therefore, a diagnosis is highly subjective and less likely to be correct.

As an example, if energy disorders were well diagnosed, why has the incidence of these energy related diseases (Obesity, Diabetes, Metabolic Syndrome) increased significantly over the past 20-30 years?