It's time to set the record straight. The only reliable way to lose weight is to eat less or exercise more. Preferably更适宜，较好 both. So why bother to state the obvious? Because a body of scientific literature has arisen over recent years, suggesting that fat oxidation氧化 – burning the fats we eat as opposed to the carbohydrates碳水化物 – is enough to promote fat loss. It isn't.

Sydney scientists have demonstrated that mice genetically² altered to burn fats in preference to优先于 carbohydrates¹, will convert the unburned carbohydrates into stored fat anyway, and their ultimate weight and body composition will be the same as normal mice.

It all comes down to an enzyme酶 known as ACC2 (acetyl-CoA carboxylase碳酸醇素), which controls whether cells burn fats or carbohydrates. When it was shown that 'blocking' ACC2 will force cells to burn fats in preference to carbohydrates, many assumed that such 'fat burning' could make fat stores evaporate蒸发，挥发, and make people thin without changing food intake食物摄取 or energy expenditure能量消耗.

Associate Professor Greg Cooney, from Sydney's Garvan Institute of Medical Research, discusses misconceptions迷思概念，错误的想法 surrounding ACC2 in findings that appear in the prestigious有名望的 international journal, Cell Metabolism⁷, online today.

"Our data urges a correction in people's concept of a magic bullet - something that will miraculously⁸ make them thin while they sit on the couch watching television," said Professor Cooney.

"While none of the large pharmaceutical⁹ companies have marketed ACC2 inhibitors, there are many kinds of so-called 'fat-burning pills' available in the health food, body building and alternative medicine markets, where limited clinical effectiveness data are required."

"Many such products can also contain potentially harmful stimulants¹⁰ or come with a recommendation to follow a calorie-controlled diet and do more exercise while taking them. If you follow those recommendations, then of course you'll lose weight - but you'd lose it anyway."

"The energy you use in your home can come from a coal-fired power station, hydroelectric power水力发电, or a wind turbine风力涡轮机. You won't know which because the end result is electricity."

"The energy that fuels your body can come from fats, proteins or carbohydrates. You won't know which because the end result is ATP, or cellular¹¹ energy."

"Your body will use the energy it needs and store the leftover¹² fats, proteins or carbohydrates as fat. When you do the sums, it's ultimately a matter of calories in and calories out."

"It's important to stress that the focus of our study was limited to an analysis of the impact of fat oxidation on overall fatness. We didn't investigate all impacts of fat oxidation – and so we don't rule out benefits of burning off fats in specific tissues."

"For example, manipulating fat metabolism脂肪代谢 may - or may not - lead to better insulin胰岛素 action in muscles or in the liver. Should insulin action be improved, that would obviously benefit obese¹³肥胖的 people with Type 2 diabetes¹⁴. But we can't comment either way until we do the experiments."

And the take-home message? Follow a healthy, balanced diet and get plenty of exercise.