Obesity and Fat Metabolism

Obesity is defined as the excessive accumulation and storage of body fat, usually measured by the body mass index (BMI) system. Your BMI is a body weight to height ratio and is calculated by dividing your weight (kg) by the square of your height (m). Refer to the online BMI calculator to work out your body mass index. While the BMI is not the most accurate method of assessing weight management problems, it is nevertheless the universal measure of assessing a healthy body weight.

Obesity predisposes you to a number of chronic conditions including diabetes, cardiovascular diseases like hypertension, musculoskeletal problems and depression. The impact of excess body fat on the human body can contribute to many other conditions, many of which are fatal and for this reason, obesity is classified as a disease. Most importantly, obesity reduces your quality of life, preventing you from doing the things you enjoy and making the most of every day.

Apart from thyroid disorders and a few other medical conditions, obesity can be treated, cured and prevented. The prevalence of obesity in South Africa today, is a combination of poor knowledge of foods, a lack of exercise and ignorance about the dangers of this disease.

How does fat store in the  body?

There are three main types of foods – carbohydrates, protein and fat. Each of these foods have a different effect on fat metabolism but all can contribute to weight gain. When you eat, food is broken down in the gut and absorbed into the blood stream. The body uses these foods for either fuelling the body by producing energy or building the body structure. If there is an excess of any type of food, the body will store this as fat.

Which foods cause fat storage?

All foods can contribute to fat storage but carbohydrates are by far the biggest culprit. Foods vary in their carbohydrate, protein and fat content although a food is usually referred to by the most abundant component. Most diets are abundant in carbohydrate-rich foods, like sugar to breads, pasta, rice and maize. Carbohydrates are broken down into simple sugars, like glucose, in the body and if there is an excess of glucose in the blood, the body secretes the hormone called insulin.

Insulin removes excess glucose from the blood by ‘forcing’ the body cells to take in more glucose, storing excess glucose in the liver and converting the remaining glucose into fat. An excess of protein rich foods, like meat, dairy and soya, will also be broken down and stored as fat although this occurs to a lesser degree than in carbohydrates.

The energy potential of foods are referred to as calories (more correctly kilocalories or kCal) or in South Africa, kilojoules (kJ). Our energy usage for daily functioning is also calculated in kJ or kCal. In an ideal situation, our calorie intake from foods would be equivalent to our calorie usage for our daily activities. If you use or burn more calories than you ate, then you would lose weight. If you eat more calories than you burn, then you will gain weight.

This is the simplest, yet most important, concept behind weight management.

Which are the fat burning foods?

This is a controversial topic because there is no foods that will actually ‘burn’ your fat. Rather the focus should lie on exercise and activity along with sensible eating to reduce fat accumulation. Certain foods are less likely to be stored as fat due to their chemical structure but an excess of any type of food will result in fat accumulation. Similarly, an active lifestyle will ensure that your body uses all the calories that you consume in a day and additional activity will cause the pre-existing fat to ‘burn’ for the body’s energy needs.

Apart from limiting portion sizes and eating low calorie foods, the other important consideration is the type of carbohydrates you consume. This is measured by the glycemic or glycaemic index (GI) and depending on the GI of the foods you eat, the body will either utilise it slowly over a period of time for energy (without storing it as fat) or it will quickly ‘push’ the food into fat storage.

How do I lose weight?

The simplest way to lose weight is to reduce your food intake (calories are more important than just portion sizes) and increase your daily activity by cardiovascular exercise. This is the tried and tested method for weight loss and there is no need for herbal concoctions, weight loss pills or fad diets. Joining a weight loss support group is often helpful in finding and relating to people with a similar problem.

The rising incidence of obesity in South Africa is evident in the increasing rates of diabetes and heart disease in the country. Without a proper knowledge of healthy eating and an active lifestyle, obesity and related diseases will be just as much of a challenge for the health sector as HIV/AIDS in South Africa.