I've been eating a high-Fat,carbohydrate(碳水化合物)-restricted diet for almost 20 years,since I started as an experiment when investigating nutrition research for the journal Science. I find if s easy for me to keep a healthy weight when I eat this way. But even after two decades, the feeling of being on the edge of a slippery slope is ever- present.

Researchers are generally divided on why we often fail to stay on diets and what causes obesity. The conventional thinking, held by the large proportion of the many researchers, is that obesity is an " energy balance" disorder,and so the treatment is to consume less energy ((fewer calories) ) and spend more. When we fail to keep this prescription, it suggests that we simply lack will power.

The minority position in this field—one that Dr. Ludwig holds, as do I after years of reporting—is that obesity is actually a hormondal(激素的)regulatory disorder, and the hormone that controls this process is insulin (胰岛 素).It signals fat cells to gather fat,while telling the other cells in our body to bum carbohydrates for fuel. By this thinking these carbohydrates, particularly grains, known as high GI carbs, as well as sugars are likely to make you fat.

"Raise insulin levels even a little" , says Dr. Robert Lustig, a professor at the University of California, San Francisco,"and the body switches over from burning fat for fuel to burning carbohydrates. Once people who are 'carboholics^,' get their insulin levels down, they become less carboholic. And if they start eating carbs, they go right back to where they were before. " Researchers like Dr. Ludwig and Dr. Lustig believe that a person can minimize these carbohydrate desire by eating lots of healthful fats instead.

Finally, any successful diet is by definition a long-term commitment. If we buy into the logic of carb -restricted diets, then it implies acceptance of a lifetime restriction.

Eating a diet high in processed (加工的) food increases the risk of depression (沮丧抑郁), research suggests. What's more, people who ate plenty of vegetables, fruit and fish actually had a lower risk of depression, the University College London team found.

Data on diet among 3, 500 middle-aged civil servants were compared with their emotional state five years later, a British journal reported. They split the participants (参与者) into two types of diet--those who ate a diet largely based on whole food, which includes lots of fruit, vegetables and fish, and those who ate a mainly processed food diet, such as sweetened desserts, fried food, processed meat, refined grains and high fat dairy products. After accounting for factors such as gender, age, education, physical activity, smoking habits and chronic diseases, they found a significant difference in the future depression risk with the different diets.

Those who ate the most whole food had a 26% lower risk of future depression than those who ate the least whole food. By contrast, people with a diet high in processed food had a 58% higher risk of depression than those who ate a diet low in processed food.

Study author Dr Archana SinghManoux pointed out there was a chance the finding could be explained by a lifestyle factor they had not accounted for.

“There was a paper showing a Mediterranean diet was associated with a lower risk of depression, but the problem with that is if you live in Britain, the likelihood (可能性) of you eating a Mediterranean diet is not very high.”

Dr Andrew Mcculloch, chief executive of the Mental Health Foundation, said, "this study adds to an existing body of solid research that shows the strong links between what we eat and our mental health.”

He added people’s diets were becoming increasingly unhealthy. The UK population is consuming less nutritious, fresh produce and more saturated (含饱合脂肪酸的) fats and sugars.