Obesity, the curse in society
One of the recurrent menaces of our time is excess weight. It is discussed in many forums, there are many solutions that have been suggested, but the weight never goes away.
Obesity is defined as 25 per cent or greater total body fat in men, and 35 per cent or greater total body fat mass in women.
Percentage body fat can be determined by measuring skin-fold thickness, biometrical impedance or under water weighing.
However, the most common method is the BMI measurement (weight in kg/height squared in metres). A BMI of between 18 and 25 is normal, 26 to 29 is overweight and above 30 is obese.
Intake of carbohydrates, fats and proteins provides energy in the body that is used to perform various functions and can be stored for later use.
For a stable body weight and composition over a long period of time, energy intake and expenditure must be balanced. If energy intake exceeds expenditure, the extra energy is stored as fat hence increase in body weight.
When energy intake is insufficient to meet body metabolic needs, the result is starvation and loss of body mass.
Different foods contain different proportions of carbohydrates, proteins, fat, vitamins and minerals, therefore there’s need for an appropriate balance so that all the body needs are provided for appropriately.
One gramme of carbohydrate releases 4.1 calories, one gramme of fat releases 9.3 calories and a gramme of average dietary protein releases 4.35 calories of energy.
There’s a high proportion of protein and fat in meat products, and a high proportion of carbohydrates in most grain and vegetables.
Fat usually exists as 100 per cent fat whereas carbohydrates and proteins are mixed in a watery media so that they normally represent less than 25 per cent of the weight.
The body has short and long term control systems to regulate food intake, energy expenditure and storage. The hypothalamus, which is a part of the brain, has both a feeding centre and a satiety centre.
Once you have eaten enough food, the satiety centre is stimulated by chemicals released from the gastrointestinal tract, from nutrients in food and the adipose tissue (fat deposit) and inhibits the feeding centre.
The hypothalamus also regulates release of hormones that affect energy balance and metabolism. Damage to these areas of the brain will result in over or under-eating.
As adipose tissue increases, it produces a chemical called leptin which stimulates the satiety centre and reduces feeding.
It is postulated that in some obese individuals, the effect of leptin on the brain is diminished, and therefore there’s continued over-feeding despite excess amounts of adipose tissue.
The causes of obesity are usually multiple and intertwined. Genetic abnormalities in the pathways that regulate feeding and also in energy expenditure and fat storage can lead to obesity.
Families also tend to have similar feeding and physical activity behaviours. Lack of physical activity and excessive eating (beyond energy requirements) also lead to weight gain. Feeding behaviour can be attributed to environmental, social and psychological factors.
There has been an increase in high-energy, processed foods with urbanisation and reduced physical activity, leading to a rise in obesity. Some people also eat more during or immediately after stressful situations.
Obesity has been associated with quite a number of health issues including low self esteem, depression and social isolation, respiratory problems, hypertension, Type II diabetes, stroke, heart attack, gall stones, fatty liver, arthritis, reduced fertility and various cancers (uterus, breast, colon).
Management primarily involves increase in physical activity and decrease in calorie intake, and this should be maintained over time.
Other measures include using drugs e.g. drugs that reduce absorption of fat from the intestines (side effects include bloating and diarrhoea) and amphetamines which inhibit the feeding centres and increase activity (side effects include over excitement of the nervous system leading to anxiety and elevated blood pressure, plus the body soon becomes used to them).
Gastric bypass surgery with stapling of the stomach and gastric banding can be done to reduce the capacity of the stomach and reduce food intake. Liposuction can also be done to reduce the amount of fat tissue.