Overweight / obesity is the causative factor for several chronic non-communicable diseases including heart disease, diabetes and certain types of cancers
There is no clear definition of a desirable or ideal body weight. Body weight for a given height of person with good health and long lifespan is considered as Ideal body weight. A much simpler and more acceptable measure is the ratio of weight and height, which estimates total body mass and correlates highly with the % of body fat. The most commonly used ratio is the BMI. It is computed by dividing the weight in kilograms by the square of the height in meters [BMI = Weight (kg) ÷ (Height in m)2]. The ideal ranges of weights for a given height are provided by WHO which is useful for categorizing persons as normal (ideal), undernourished and overweight or obese.
Definition of obesity is based on the degree of excess fat. More than a general accumulation, the distribution of fat around the abdomen is now considered to be more harmful than fat around the hips. Accumulation of fat around abdomen indicated by higher waist circumference is considered as risk factor. In general, BMI ranging from 18.5 to 25 is considered to be normal. However, for Asians it is recommended that the BMI should be between 18.5 and 23, since, they tend to have higher percentage body fat even at lower BMI compared to Caucasians and Europeans, which puts them at higher risk of chronic non-communicable diseases.
The cut-off levels for categorizing overweight and obesity in children and adolescents are different. =5th and <85th centiles are normal, and with =85th and <95th centile are considered as overweight. More than 95th centile are considered as obese.
The waist circumference and waist-to-hip ratios are useful for estimation of central and truncal obesity respectively. Several studies have shown that the central obesity was directly correlated with chronic degenerative diseases especially metabolic syndrome. Waist-to-hip ratio of more than 0.9 among men and 0.8 in women and waist circumference 90cm for men and 80cm for women are associated with increased risk of several chronic diseases especially in Asian Indians.
There are several health consequences of obesity. Excessive body weight increases the risk of heart disease, hypertension, diabetes, gallstones, certain types of cancers and osteoarthritis. Obesity invariably predisposes to reduced levels of high density lipoproteins ('good' cholesterol) and to increased levels of low density lipoproteins ('bad' cholesterol), and triglycerides, besides an abnormal increase in glucose and insulin levels in blood. Considering the increasing trend in the prevalence of coronary artery disease, hypertension and diabetes in India, it is important to maintain desirable body weight for height and avoid obesity.
Over-feeding during infancy, childhood and adolescence predisposes to overweight/ obesity during adulthood. The tendency of familial obesity seems to be inherited. Eating junk or unhealthy foods coupled with low physical activity is considered as a main contributor. Complex behavioral and psychological factors influence the eating patterns. In addition, metabolic errors in energy utilization may favor fat accumulation. Insulin is an important modifier of energy and fat metabolism favoring fat deposition. Low and high birth weight (<2500 g and >3500g), obesity during childhood and adolescence are likely to lead to obesity in adults. It is therefore, necessary to maintain a desirable body weight by consuming just enough calories or adjust physical activity to maintain energy balance (intake = output). Body weight must, therefore, be checked and monitored periodically.
Several studies have suggested that hours spent in watching television is strongly associated with weight gain in childhood and adolescents, mostly due to the sedentary behavior, tendency to consume snack foods while watching television and influence of the advertisements of energy dense foods.
Adults usually tend to gain weight between the ages of 25-50 years. In women, obesity develops just around pregnancy and after menopause.
There is no single regimen for weight reduction; it has to be individualized. Weight reduction should be gradual. Weight reduction diets should not be less than 1000 Kcal/day and provide all nutrients. A reduction of half a kilogram body weight per week is considered to be safe. Extreme approaches should be avoided and use of drugs may be dangerous. In children, obesity should be controlled by increasing physical activity rather than restricting food intake. Modifications in dietary habits have to be incorporated into one's lifestyle along with adequate exercise to keep the body weight within the normal limits.
As fat contains more than twice the calories (9Kcal) per gram compared to protein (4Kcal) and carbohydrate (4Kcal), weight reducing diets should limit the fat intake. Refined sugars (4Kcal) and alcohol (7Kcal) provide empty calories and should be avoided. Refined carbohydrates which promote fast absorption of glucose (Glycemic carbohydrates) also need to be restricted. Plant foods that provide complex carbohydrates and fibre may be preferred as they reduce blood glucose, cholesterol and triglycerides. Weight- reducing diets must be rich in proteins and low in carbohydrates and fats. Consumption of plenty of fruits and vegetables would not only result in satiety but could also help to maintain adequate micronutrient intake. Frequent fasting/ semi-fasting (cyclic weight reduction) followed by adequate or excess food consumption will also aggravate the problem of weight gain. All reducing regimens should be monitored by a doctor and a dietitian.