Obese and overweight people require more fuel to transport them and the food they eat, and the problem will worsen as the population literally swells in size, a team at the London School of Hygiene & Tropical Medicine says. This adds to food shortages and higher energy prices, the school's researchers Phil Edwards and Ian Roberts wrote in the journal Lancet on Friday. "We are all becoming heavier and it is a global responsibility," Edwards said in a telephone interview. "Obesity is a key part of the big picture."