There are main contributing factors to obesity but generally caused by eating too much and lack of physical activity, genetics and taking certain medications can also play a role. Obesity results when the consumption of food exceeds the body’s need for energy. To say that obesity is caused by overeating and inactivity, however, is an oversimplification of a much more complex problem.
After years of research, scientists still do not know exactly why some people seem to have no trouble with weight control. While others must continually “battle the bulge.” Many complex factors are involved. These include heredity, metabolic function, efficiency of energy utilization, hormonal function, appetite regulation, eating behaviour, dietary patterns, lack of exercise, life style, and possible personality and emotional problems.
Familial Factors Contributing to Obesity
Familial factors are known to be very important in relation to the occurrence of obesity. For example, children of two obese parents are three times as likely to be fat as children of two non obese parents. This familial influence could either be environmental and related to eating habits and dietary patterns in the family, or genetic in origin.
What causes this similarity? One cause is our inherited body type or shape. Body shape may be divided into three classifications: endomorphic (plump and round), mesomorphic (muscular), and ectomorphic (thin and bony). Most of us are a blend of all three types with a tendency toward one or two types.
Because the soft tissues of endomorphs have a greater fat storage capacity, these types tend to gain weight much more easily than their ectomorphic friends, whose stringy tissues have a low-fat storage capacity. The fat storage capacity of the mesomorph is greater than that of the ectomorph, but less and more evenly distributed over the body than that of the endomorph.
Genetic and Environmental Factors Contributing to Obesity
A factor that may have both genetic and environmental roots is our capacity for storing fat. Obesity can result either from too many fat cells or a normal number of oversized fat cells. Although recent evidence indicates that the fat cells of some people may divide and multiply at any time throughout life.
The most critical periods of fat cell multiplication appear to be the third trimester of pregnancy, the first 2 to 3 years of life, and adolescence. For this reason, persons who become obese during childhood often have an overabundance of fat cells whereas those who gain most of their excess weight later in life have a normal number of extra-large fat cells. Unfortunately, one does not lose fat cells during weight loss, but merely depletes their size.
Factors Contributing to Obesity in Childhood
Although there is some evidence that obesity starting in childhood is more difficult to treat, this has not yet been established. It is not true that fat babies will necessarily become fat adults, nor that formula-fed infants are more likely than breast-fed infants to become obese in later life. It is important that parents do not overreact to concern about obesity in feeding their children.
Growth retardation due to malnutrition has been reported to occur as result of a self-imposed calorie restriction on young children arising out of a fear of future obesity. In addition, eating disorders such as anorexia or bulimia. Especially in young women, appear in part to develop secondary to a preoccupation with thinness.
Energy Balance and Obesity: What are the Main Drivers?
Efficiency of energy utilization is another factor which plays an important role in the development of obesity. Energy expenditure may be somewhat arbitrarily divided into three components:
- Basal metabolism, that is, calories expended at rest and in a fasted state,
- Additional calories required to metabolize food, and
- Calories burned during physical activity, ranging from sedentary activity to highly vigorous exercise.
For many of us, basal metabolism and sedentary activity account for most of our energy needs. The number of calories spent per day for these needs appears to vary widely, depending on such factors. As the shape and composition of our body, our gender, and the amount of food we eat. For example, basal metabolic rate is 10% higher for men than women. It is also higher for lean people and for larger people with more surface area of either sex.
Diet also appears to cause differences in energy expenditure among people. Unfortunately, calorie restriction has been shown to produce decreases in basal metabolic rate of 15 to 30%. Decreases in spontaneous activity, and decreases in the energy cost of a particular task.
Prevalence
A variety of appropriate height/weight standards are used to assess the incidence of obesity or overweight.
Estimates on the percentage of people who are considered to be obese or overweight vary considerably for several reasons. Different measures for measuring fatness produce variable results. Also, there is disagreement on what the appropriate weight standards should be.
Height-weight charts are the most common method of estimating desirable body weight. In some cases, height-weight charts may be misleading. Obesity means having an excess proportion of fat tissue in the body, not just being overweight for one’s height and body build. For example, football linemen are always overweight but rarely overfat. On the other hand, it is quite possible for sedentary persons to be overfat but not overweight for their height. For most individuals, however, being overweight implies being overfat and hence obese.
