A Daily news digest by Jasper van Santen

A Mathematical Challenge to Obesity – NYTimes.com

In News, Nonsense on May 16, 2012 at 02:56

A Mathematical Challenge to Obesity 

Beginning in the 1970s, there was a change in national agricultural policy. Instead of the government paying farmers not to engage in full production, as was the practice, they were encouraged to grow as much food as they could. At the same time, technological changes and the “green revolution” made our farms much more productive. The price of food plummeted, while the number of calories available to the average American grew by about 1,000 a day.

Well, what do people do when there is extra food around? They eat it! This, of course, is a tremendously controversial idea. However, the model shows that increase in food more than explains the increase in weight.

In the 1950s, when I was growing up, people rarely ate out. Today, Americans dine out — with these large restaurant portions and oil-saturated foods — about five times a week.

Right. Society has changed a lot. With such a huge food supply, food marketing got better and restaurants got cheaper. The low cost of food fueled the growth of the fast-food industry. If food were expensive, you couldn’t have fast food.

People think that the epidemic has to be caused by genetics or that physical activity has gone down. Yet levels of physical activity have not really changed in the past 30 years. As for the genetic argument, yes, there are people who are genetically disposed to obesity, but if they live in societies where there isn’t a lot of food, they don’t get obese. For them, and for us, it’s supply that’s the issue.

Interestingly, we saw that Americans are wasting food at a progressively increasing rate. If Americans were to eat all the food that’s available, we’d be even more obese.

Any practical advice from your number crunching?

One of the things the numbers have shown us is that weight change, up or down, takes a very, very long time. All diets work. But the reaction time is really slow: on the order of a year.

People don’t wait long enough to see what they are going to stabilize at. So if you drop weight and return to your old eating habits, the time it takes to crawl back to your old weight is something like three years. To help people understand this better, we’ve posted an interactive version of our model at bwsimulator.niddk.nih.gov. People can plug in their information and learn how much they’ll need to reduce their intake and increase their activity to lose. It will also give them a rough sense of how much time it will take to reach the goal. Applied mathematics in action!

What can Americans do to stem the obesity epidemic?

One thing I have concluded, and this is just a personal view, is that we should stop marketing food to children. I think childhood obesity is a major problem. And when you’re obese, it’s not like we can suddenly cut your food off and you’ll go back to not being obese. You’ve been programmed to eat more. It’s a hardship to eat less. Michelle Obama’s initiative is helpful. And childhood obesity rates seem to be stabilizing in the developed world, at least. The obesity epidemic may have peaked because of the recession. It’s made food more expensive.

You said earlier that nobody wants to hear your message. Why?

I think the food industry doesn’t want to know it. And ordinary people don’t particularly want to hear this, either. It’s so easy for someone to go out and eat 6,000 calories a day. There’s no magic bullet on this. You simply have to cut calories and be vigilant for the rest of your life.

 

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