England, for all its independence catches a cold when the US sneezes. From economy to culture, England absorbs elements of its ally over the pond. Obesity in the US has increased yearly for the last 15 years to the point where 64% of the adult population is overweight, and just over a quarter are clinically obese. In comparison, in England 46% of men, and 32% of women are overweight with a further 17% of men and 21% of women being obese. These numbers are a damning insight into the lifestyle and diet of the nation in the modern world. What is happening to our bodies? Maybe the biochemistry of obesity might shine a light on the situation.
One pound of human fat is the equivalent to 3500 calories, or 7 large milkshakes at McDonalds. In mathematical terms, one could assume that if I were to increase my milkshake intake by 2 a week, in less than a month I’d gain a lb of fat. However, this isn’t biologically correct. The body has the capacity to match our energy output, such as exercise and our basal metabolic rate, to our energy input, our diet. In a normal situation your body will work hard to keep your body fat within a certain healthy range. A Cambridge study from 1992 shows exactly that; two groups of volunteers were split into “overweight” and “lean”, and both groups made to eat 50% more calories than their daily needs for 6 weeks in controlled conditions. Unsurprisingly, both groups underwent excessive weight gain, predominately fat. After these 6 weeks, both groups were then asked to return to normal eating habits. Lo and behold, both groups lost a significant amount (61%) of the fat mass they had accumulated, telling evidence that the body has no desire to keep body fat high. So how has it gone so wrong?
A biochemical malfunction may give an interesting insight into how we can override our body’s natural desire for limited fat. Adipose tissue (tissue composed of fat cells) is part of the endocrine (hormone producing) system, not just a bit of blubber. One of the hormones it produces, leptin, is essential for fat regulation. Leptin has a number of fat burning physiological effects, from decreasing appetite to triggering fat breakdown. This is the body’s fat feedback system, so the more adipose cells, the more leptin you have in the body and hopefully the more fat burning, keeping the body in a nice equilibrium. Consider mice with the leptin gene knocked-out become vastly overweight due to uncontrolled eating as good evidence.
Leptin’s main site of action is in the hypothalamus, located in the brain just above the brain stem. Upon leptin binding, it controls energy expenditure, appetite and insulin sensitivity (the more insulin sensitive you are, the less insulin required to lower blood sugar and therefore less fat gain). Furthermore, it has been shown in rats and mice that leptin resistance in the hypothalamus causes obesity; it is very likely that this is true of humans as well. So what causes leptin resistance? There are a number of probable causes, two of which look interesting. Firstly, hypothalamus inflammation appears to stop leptin from working and secondly, not enough leptin passing into the brain. These are not mutually exclusive, but what is causing this? A genetic cause is very unlikely for the vast majority of cases because of the sheer numbers of overweight and obese people, so there must be another cause. This cause must be relatively new to humans since such widespread obesity is a very new human phenomenon.
The standout candidate for this would be the shift of our diet. Recent diet changes such as an increased intake of processed carbohydrates (like refined sugar and fructose syrup); decreases in our fibre intake and not enough vitamins in our diet – which can cause abnormal “friendly” bacteria growth and an increase in gut permeability. Both of which appear to increase the number of inflammatory agents in the body, which in turn may lead to hypothalamus inflammation.
The quality of our food has taken a turn for the worse as well; along with the terrible refined sugars which litter our food, we have terrible quality fats. Less omega-3 fatty acids and more processed omega-6s have lead to an imbalance in the ratio. There are a number of studies which show that omega-3 deficiencies lead to leptin resistance, and diets with high omega-3, even with plenty of other fat, show decreases in leptin resistance. There is a link between the two; humans on the whole have moved away from what is arguably our natural diet. Lots of fruit, vegetables, protein and natural food sources. We have started to treat our bodies as rubbish bins rather than organic beings.
What of the future? Obesity is still rising in England, despite the best efforts of the healthcare system and TV chefs. Education is the only way to stop this. Gastric bypasses, pharmaceutical drugs like Alli, and fad diets will have no significant beneficial effect. People need to learn to eat again, head back towards the natural diet of our species and care for themselves. Fruit and vegetables aren’t expensive, so next Tuesday pick-up a few more apples and carrots at the market.