We produce too much food.
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Kevin Hall
Senior investigator at the National Institute of Diabetes and Digestive and Kidney Diseases

Back in the 1990s, executives at a Bay Area biotech hired Kevin Hall away from the physics department of McGill University to create a computer simulation of type 2 diabetes. That career change eventually led to his current position as senior investigator at the National Institute of Diabetes and Digestive and Kidney Diseases, where he has created a mathematical model to help resolve the obesity debate. "There was all this data out there in nutrition and metabolism research, but putting the data together so you could really understand the whole system in an integrative way and be able to make predictions – that was missing. That's what we're bringing to the table," he says.

While most experts are trying to figure out why we're fat, Hall is trying to understand why we're not fatter. After crunching available data on obesity, including food-production statistics, he concluded that the U.S. produces 750 more calories of food per person today than it did in the 1970s – an excess that, if we consumed it every day, would have turned us all into blimps. "I was mystified that we weren't more obese," he says. What's saved us from a greater degree of fatness can be found in our country's landfills as food waste. Yet we still consume about a quarter of those excess calories, which is why the average weight of men in the 1970s – 169 pounds – has turned into the average of 190 pounds today.

Hall is enlisting his math machine to help settle the biggest debate in weight loss: Should we reduce calories to shed weight, as Bray thinks, or eliminate sugar and carbs, as Taubes believes? His lab is also conducting experiments, feeding subjects a low-fat or a low-carb diet with the same number of calories. "If it's not true that 'a calorie is a calorie,' I want to find out just how far off it is," he says.