Are certain people destined by their genes to be overweight or obese? The numbers vary greatly, but the heritability of body fat mass and body fat percentage is estimated at around 50%. That means our parents are only partly to blame for our size. Environmental factors, which are within our control, take half the blame.

Medical Causes

Some medical conditions are associated with weight gain. Examples are hypothyroidism (low levels of the thyroid hormone result in a lower metabolic rate), Cushing’s disease (the adrenal glands overproduce corticosteroid, which stimulates the deposition of fat) and genetic disorders such as Prader-Willi, Bardet-BeidI, Cohen and Alstrom syndromes. The consumption of certain drugs, such as glucocorticosteroids (sometimes found in traditional medicines), oral contraceptives and antipsychotics, can also cause weight gain. Collectively, medical conditions and drugs are the cause of obesity in less than 5% of cases.

If you are very obese or are gaining weight despite maintaining a healthy diet and exercise regime, it is a good idea to see your doctor to exclude the above conditions.

Lifestyle Factors

What then are the causes of obesity in the more than 95% of cases? Don’t blame it on “slow metabolism”. Lifestyle factors, such as sedentarism and a high intake of energy-dense food, are to blame. Our environment has a bigger effect on our weight than we would like to think.

In the past, when transportation networks were less efficient and fewer things were automated, people could not avoid being physically active.

Today, we have cars, car washes, elevators, escalators, travellators, golf buggies, washing machines, vacuum cleaners, motorized lawnmowers and many more machines to spare us the physical exertion. It has been estimated that Australian farmers in the outback took 20,000 steps per day and hunter-gatherers in tribal societies took 30,000 steps per day.

How many steps do you think the average city dweller who drives daily to an office job takes a day? Only about 3,000! Some housewives who enrolled for a weight loss program recently recorded taking fewer than 2,000 steps per day before they started making positive changes to their lifestyles!

We have always been paid for providing manual labor. Today, we pay for the opportunity to do manual work – we pay membership fees to use the gym!

With fancy restaurants, mega food courts, fast-food outlets, take-away outlets, home-delivery services, 24-hour convenience stores and even mobile food vans, food has become extremely accessible. In fact, it is hard to avoid food. Not only is food easily available and intensively marketed, but serving sizes are also increasing. Drinks come in super-sized cups, snack foods such as chocolates and potato chips are packaged with an extended portion marked “Extra 20% free!”, more and more restaurants are jumping on the all-you-can-eat bandwagon and value meals and “upsize” offers encourage customers to eat out and eat more!

A 2004 article in the National Geographic magazine showed that in 1954 a hamburger from a popular fast-food chain weighed 80 g and contained 202 kcal compared to 122 g and 310 kcal in 2004; French fries from another fast-food chain weighed 68 g and contained 210 kcal in 1955 versus 198 g and 610 kcal in 2004. Food that is bad for us is cheap, intensively marketed and made to taste good while healthy food (such as brown rice and lean cuts of meat) is costly, not promoted and not so easily available.

Give a little thought as to where and how you eat the majority of your food, and try to incorporate more steps into your day – see my recent post – Walking For Weight Loss – for more info.