Americans have gained a lot of weight in the past few decades. Is it our sedentary lifestyle? The increase in processed foods and sweeteners? Supersized portions? Researchers from the World Health Organization in Australia say it’s very simple: we eat too much. They presented their findings May 8th at the European Council on Obesity.

Scientists measured the metabolism of almost 1,500 adults to determine how many calories their bodies burn under normal conditions. Then they calculated how many calories they’d need to maintain body weight. They figured out how much we’re eating today versus three decades ago by comparing agricultural data from then and now. They determined total food grown and imported, minus what was exported, thrown away or used for livestock.

With that information, they predicted how much fatter we should be based just on consumption. And we’ve actually gained a little less than the numbers say we should have. Maybe because we’ve added some exercise to the equation.

The scientists say this study shows that the situation is straightforward. Exercise is great, but to get the weight down, Americans have to adopt the ELF diet. Where ELF stands for eat less food.

—Cynthia Graber