Whether we are under or over weight is not just an individual cosmetic issue. Extremes of body weight are a universal concern, giving rise to health risk and chronic diseases.
Being excessively overweight is an underlying risk factor for heart disease, high blood pressure, and diabetes.
The relationship between excess weight and disease is serious and undisputed, a significant concern as obesity continues to increase in prevalence.
People who are underweight may suffer from a weakened the immune system, nutrient deficiencies, and an increased risk of osteoporosis.
Both conditions result in a lack of energy and reduce life expectancy.
Even a small amount of extra body weight enahnces our risk of disease and affects longevity.
Insurance companies recognised that weight was a predictor of health years ago, with increased weight and girth resulting in higher mortality. From the data they pooled, charts were developed to define body weight in relation to health risk and estimated longevity.
This led to the creation of the Body Mass Index, which defines our ideal weight, at which we can expect to live a longer, healthier life.
The body mass index (BMI)
BMI is used to define the categories of being underweight, normal, overweight, or obese. It is the accepted method of determining risk potential for disease.
BMI may not be accurate for people with a high muscle mass (such as body builders), but it serves as an easy, reliable indicator of health risk calculated from measuring height and weight.
The greater your weight compared to the square of your height, the greater your BMI, and the greater the health risks.
How to calculate your BMI
Body Mass Index = W/H2
For example, a woman weighing 65kg (10 stone 5 lb), who is 1.70m (5 ft 5 inches) tall, would have a BMI of 22.5 kg/m2
This is worked out by carrying out the following calculation:
65 divided by 1.702 = 22.5
Now you know your Body Mass Index - how do you fit into the national picture?
3 in 5 adults are overweight
1 in 6 men and 1 in 5 women are obese, obesity being most prevalent in the 45-64 year olds.
The number of people classed as overweight or obese in the UK has steadily increased over the last two decades.
A useful alternative to BMI is the waist:hip ratio, also known as WHR, which relates to the distribution of body fat.
WHR predicts health risks such as cardiovascular disease and diabetes by determining whether you are centrally obese, and what shape your body is.
When fat accumulates around your abdomen, you are said to be apple shaped. This indicates central obesity, and a greater risk of disease. Fat stored on the hips and thighs makes you pear shaped, and your risk of disease is lower.
To work out your WHR, you need to first take some measurements. Measure your waist at its narrowest point (at the navel) and divide this number by the measurement of your hips at their widest point (over the buttocks). The resulting figure is your WHR.
For example, 36 divided by 38 = 0.95. 0.95 is the WHR.
Central obesity (or being apple shaped) is defined when WHR exceeds 0.95 for men, and 0.79 for women.
Apple shaped men = WHR greater than 0.95
Apple shaped women = WHR greater than 0.8
Pear shaped men = WHR less than 0.95
Pear shaped women = WHR less than 0.8
Why such an unhealthy nation?
With the mass production of food products and change in consumer habits, it is easy to see why we are an overweight nation.
Over-indulgence has become commonplace since cultivated cereals became available some 12,000 years ago. Today's consumption of energy-dense, palatable foods which are higher in fat and sugar has compounded the problem.
Our modern diet is a continual feast in comparison to the hunter-gatherers' existence on meat and seasonal fruits and vegetables, for which we were well-adapted.
Man evolved to tolerate periods of food restriction and relative excess. The efficient burning of calories in the metabolism of our ancestors enabled them to survive periods of starvation.
That same adaptation now underlies much disease in western society.
In addition, physical activity has decreased as the use of motorised transport and the popularity televisions and computers has increased. Often the greatest exercise we get is through shopping, gardening, or housework.
We enjoy food, and there is nothing wrong with that. But adjustments to our diet and activity levels are urgently required to reduce the risk and cost of future ill-health.
MORI, Nestle Survey
Fat structure and development
When talking about body weight, we think of fat.
Calories not immediately required for energy are stored as fat in adipose tissue. This structure is like a honeycomb of large spherical cells (adipocytes) filled with droplets of fat ready to release energy when necessary.
There is a rapid deposition of fat in early infancy. The final number of fat cells, between 30 and 40 billion, are created and determined during these first years of growth. These may fluctuate in size throughout life, but not in number.
Is fat so bad?
To lose weight, we need to lose the contents of these cells. Yet without fat, human life would not exist, so we need to put it into perspective.
Fat is essential for health, acting as a protective tissue to vital organs, like a biological bubble wrap, and providing insulation to keep us warm.
It provides a source of energy which enables our survival in periods of food shortage, and hormones such as oestrogen which are essential for the good functioning of many body systems.
It plays a structural role in body cells, a high concentration being present in the brain, and is vital for the absorption and storage of the fat-soluble vitamins A, D, E and K as well as providing essential fatty acids.
Ultimately fat is an organ, part of a complex inter-connecting network.
Diets come and go. We may know what is good for us and what is not, yet excess weight gain often preoccupies. What steps can we take to assume control of this situation?
Reducing food intake and increasing exercise is still the best means to weight loss. You are more likely to develop life-long habits that you can maintain easily and enjoy if you set yourself realistic targets and lose weight slowly.
Choose an activity that you will look forward to, whether it be gardening or dancing, and adopt a strategy for reducing calorie intake that you can follow over a long period.
Without fat, food can become tasteless and without texture, and without carbohydrate, the diet can become unsatisfying.
The key is to enjoy good, healthy food and exercise.
Written by K Mellish.