- From the late 1970s to 2000s the incidence of obesity rose from 12% to 25%.
- Diseases such as diabetes have increased markedly in this period - from 5 million to 20 million.
Why Has Obesity Risen?1. Increased Consumption of Sugar / Carbohydrates
In recent decades there has been increased production of Corn syrup. Helped by government subsidies, the production of high fructose corn syrup has led to falling prices of simple carbohydrates. Basically, high calorie, high carbohydrate food has become cheaper encouraging people to consume more high calorie foods. Fruits and vegetables on the other hand have become relatively more expensive. There is an economic incentive to buy foods that are unhealthy and lead to obesity. This is why obesity is often worst in low income groups. The poor can afford food, but, they struggle to afford healthy food - buying instead cheap carbohydrates and take away McDonalds.
2. More sedentary lifestyles. With an increase in car use, there has been a corresponding declining in physical exercise such as walking to shops. 
3. Bigger Sizes. It is argued the 'super size' food portions encourage people to eat more. This is controversial, the argument against is that in the past, people would simply have bought two 'small' sizes to get one big size. However, I don't believe this. When I go to America, you get bigger portions so I eat more, when I return to England, I don't order 2 medium sized portions just so that I can get an American sized portions. We can't just blame food companies, clearly there is a demand for 'super size' foods otherwise people wouldn't order them.
The Genetic Myth.
Many argue the cause of obesity is genetic. But, if the cause of obesity is genetic why has it not been a problem until the last half of the twentieth century? The answer is that genes can make certain groups of people more susceptible to putting on weight and becoming obese. But, genes can never be the only cause of obesity; they merely make it more likely to occur for some people. Certainly the rise in obesity cannot be explained by a rapid change in the gene pool.
The Fat Myth
Ironically, America's booming obesity has been related to its growing obsession with fat intake. Low fat foods are very popular; but it appears reducing fat intake does not solve the problem of obesity, if lower fat is replaced with higher carbohydrates. Also many low fat foods are only marginally less fatty than their original sizes. The % of fat in American diets has fallen from 40% to 34% yet obesity has risen.
Solutions to Obesity1. Do Nothing. It is not unreasonable to say obesity is not the government's problem. If people choose to eat a lot of food and lead sedentary lives it is their choice - and who is the 'nanny state' to tell people how to live?
- However, the problem is that from an economic perspective obesity imposes tremendous costs of society. Costs of obesity include:
- Health costs of treatment
- Lost hours at work due to health related disease.
- Death. 400,000 deaths a year is a sobering statistics. Consider how much the government will spend on fighting terrorism which accounts for a fraction of the annual number of deaths. If your only target was to save lives, you would immediately switch resources from security measures to fighting obesity.
If high corn syrup foods cause obesity and therefore externalities to the rest of society, then it make sense to tax it. (or at the very least stop subsidies for growing high carbohyrdate foods. See: Why we should tax Unhealthy Foods.
3. Get People Out of Cars.
50% of car journeys are less than 2 miles. People have become reluctant to do any exercise and always prefer to take motorised transport. You could reduce dependence on cars by increasing taxes on petrol and raising the legal driving age. Neither would be popular; but, it would be effective in dealing with obesity. (see: Rising petrol prices reduce obesity) see: Call to ban car use to schools)
4. Legislation about Food Content and Food Sizes.
This would be rather controversial as it involves heavy government regulation on people's diet. But, limiting food sizes could be a solution.
Statistics for Obesity came from:
1) Loretta Napoleon Rogue Economics Chapter six, citing interview with Dr James Kenney
 International journal of obesity