The world is getting fatter, and packing on the pounds is not just for wealthy nations anymore. Obesity is sweeping into low and middle-income countries, reports the World Health Organization's obesity center, creating a dual problem of unhealthy weight gain in some segments of a country's population, and malnutrition in others. The warning comes as part of a special Lancet series on weight gain in the run-up to the United Nations high-level meeting on non-communicable diseases in September. World leaders will meet to plan a response to rising rates of heart disease, cancers, diabetes and other conditions closely tied to obesity. There are an estimated 1.46 billion overweight adults worldwide, and 502 million of them are considered obese. While nearly all countries are seeing rates rise, the severity of the problem varies greatly from country to country, said the WHO. In Japan, about one in every 20 adult women is obese, compared to one in four in Jordan, one in three in the United States and Mexico, and up to seven in 10 in Tonga.