Africa, a continent usually synonymous with hunger, is falling prey to obesity.

It's a trend driven by new lifestyles and old beliefs that big is beautiful.

Ask Nodo Njobo, a plump hairdressing assistant.

She is coy about her weight, but like many African women, proud of her "big bum." She says she'd like to be slimmer, but worries how her friends would react.

"Here, if you lose a lot of weight, people automatically think you have TB or AIDS. It's not like in America and Europe where you go on a diet to lose weight," Njobo said.

More than one-third of African women and a quarter of African men are estimated to be overweight, and the World Health Organization predicts that will rise to 41 percent and 30 percent respectively in the next 10 years.

"We have gone from undernutrition to overnutrition without ever having passed healthy nutrition," said Krisela Steyn, the retired director of the South African Medical Research Council's Chronic Disease and Lifestyle unit.

Although the figures are lower than in affluent countries, many experts fear that health systems already stretched by the AIDS virus, malaria and poverty-related diseases may snap under the additional burden of heart disease, strokes, cancer and diabetes, conditions linked to obesity.

Worldwide, an estimated 1 billion people are overweight, compared to 800 million who are undernourished.

Ironically, the poorest are often most vulnerable. Children born with low birth weights to malnourished mothers tend to be more at risk of becoming overweight as adults. They are also more prone to obesity as family members give them too much food to help them catch up, according to experts at a recent conference on chronic disease in Cape Town.

The problem is most pronounced in South Africa, where death rates from obesity and diabetes are on the rise.

Some 56 percent of South African women are now either obese or overweight, compared to fewer than 10 percent who are underweight. More than 17 percent of adolescents here are overweight — for teenage girls, it's 25 percent, according to the Medical Research Council.

The traditional diet is heavy in starch, with foods like maize meal and white bread being staples. Three spoons of sugar in coffee and tea are the norm. And, as elsewhere in the world, high-fat, high-sugar fast foods, snacks and fizzy drinks are in.

And, like elsewhere, growing urbanization has led to less walking and other exercise and the spread of television has led to a generation of couch potatoes rather than athletes.

In South Africa and throughout the continent, it is considered rude to refuse food.

"We face a very difficult situation in trying to manage obesity. We are up against social and traditional norms that being fat is a sign that you are wealthy, you are successful, you are happy, that your husband can feed you," Steyn said in an interview.

"Plus the trend toward less physical activity and the viewpoint that if you are wealthy you don't sweat," she added.

Njobo is typical. She comes from a remote rural village where walking was the main means of getting around. She now works in downtown Cape Town and says she doesn't have time to buy and cook vegetables and lentils so she often grabs convenience foods. She is too tired to exercise after being on her feet all day and after the long bus ride to and from the hair salon. In any case, she wouldn't dream of jogging in the poor suburb where she lives as it is plagued by high crime.

South Africa is not alone. In Cameroon, where the diet is rich in palm oil, cornflower products and red meat, 35 percent of the population is overweight or obese. Similar rates are found in Gambia and Nigeria, particularly among women, according to figures presented at a recent conference organized by the Oxford Health Alliance of health professionals and academics.

These numbers are still far below the industrialized world — only about 2 percent of Africans suffer from diabetes, compared with nearly 8 percent in Europe and North America. But the International Diabetes Federation says Africa's overburdened health systems are ill-equipped to diagnose the disease, and treatment is too expensive most of its victims.

The federation cites the example of a diabetes patient in Bamako, the capital of the desert country of Mali, needing to spend more than $21 on diabetes care a month — more than half the average family's income.

Poor communities with no electricity or refrigerators face the added problem of how to store insulin. Even in relatively sophisticated cities like Cape Town, the number of diabetes sufferers with amputated feet due to late diagnosis and poor treatment is distressingly high.

"It's not true that only the rich have problems with obesity and overweight," says Jean-Claude Mbanya, director of Cameroon's National Obesity Center.

"The poor suffer even more."