Dissatisfied with their body image, people complain to their physicians that they are either “too fat,” or their “shape is wrong.” With medical help (or a miracle) they wish to lose weight all over or only on their thighs, hips, arms or stomach. The converse also holds true. Obviously overweight people too sometimes declare, “I’m okay” and have no desire to diet or exercise.

The small minority who wish to gain weight can do it by increasing food intake at meals and snacking frequently. They too need to exercise — 20 minutes of aerobic exercise and 20 minutes of weight lifting every day.

“Looking good” or having ideal body weight is not a “feeling”. It is a scientific number based on calculations using a measuring tape and a weighing scale. The body mass index or BMI is calculated by measuring your weight in kilos and dividing it by the square of your height in metres.

BMI has its own limitations. If it is calculated for adults who are very muscular, or very thin, they may fall erroneously into the healthy category. The value is also not reliable in very short adults or pregnant women.

Between the ages of two and 20, the calculation is different. Ideal body weight has to be read off from charts. Any child over the 95th percentile is obese. Childhood obesity has to be tackled seriously. Fat children become sedentary overweight adults.

Overweight individuals may have subcutaneous fat uniformly distributed all over the body, or mainly a paunch with the fat concentrated in the stomach area. An apple-shaped body with a big stomach is more dangerous than a pear-shaped body with big hips. The waist:hip ratio can be measured to determine the health status. The normal value is less than .85 for women and less than .90 for men. A person with subcutaneous as opposed to visceral fat can have a high BMI and still fall within the healthy range for the waist:hip ratio.

The waist circumference alone can also be measured. In women, a waist circumference greater than 35 inches, and in men a waist circumference more than 40 inches is considered dangerous.

Without any equipment the “stand-up” test can be performed. The person is asked to sit on the floor and then stand up. Each manoeuvre is given five marks. If an extra part of the body like the hand or thigh is used for balance, a mark is subtracted. If there is even a transitory loss of balance, half a mark is subtracted. A healthy individual scores eight and above irrespective of age or body weight. A score of five or less indicates poor health.

The pull up test involves asking people to pull themselves up on a bar using their hands. Very fit men can do 10 of these and women around two.

Studies have now shown that all these values have to be taken into consideration to evaluate health. Once a person falls into the “unhealthy” category the risks for metabolic disorders such as diabetes, an abnormal lipid profile, hypertension, stroke and heart disease exponentially increase. The lifespan also reduces.

Weight loss is a lucrative commercial business. All kinds of fad diets are available on the Internet and in the market. They usually concentrate on removing or reducing one or the other constituent (fat, carbohydrate or protein) in the food. Meals may be replaced or supplemented with shakes and powders to help lose weight. Some advertise, “Exercise is not required”. These claims are backed up with “before and after” photographs.

Dieting alone can make you thin, but not necessarily fit. Without exercise, your ratio of fat to muscle remains the same. The dangers of obesity are still present. Keeping the weight off permanently also becomes a challenge as the abnormal meal patterns are difficult to sustain over a prolonged period. The powders provided are not only expensive, they may contain chemicals like creatinine, amino acids, hormones and sometimes even steroids.

Surgery can also be done to reduce the capacity of the stomach. Once that occurs the weight will come down but the fitness level does not necessarily improve.

This does not mean that you should not try to get your weight down to the ideal range. Extra kilos, even if you are fit, place extra strain on the heart, spine, hip and knee joints.

Exercising for 40 minutes a day will keep you mentally alert and physically fit well into a ripe old age even if you do not look thin.

Dr Gita Mathai is a paediatrician with a family practice at Vellore. Questions on health issues may be emailed to her at yourhealthgm@yahoo.co.in