Weight Loss Theories
Diet supplements are often advertised as ‘extreme fat burners’ or ‘craving quashers’. But evidence used to support these claims simply doesn’t add up, a leading U.S nutrition expert has warned.
Professor Melinda Manore from Oregon State University analysed the research used to support hundreds of diet pill claims.
She found no evidence that any single product was a 'wonder pill' causing significant weight loss and found some even had detrimental health effects.
'What people want is to lose weight and maintain or increase lean tissue mass,' Prof Manore said.
'There is no evidence that any one supplement does this. And some have side effects ranging from the unpleasant, such as bloating and gas, to very serious issues such as strokes and heart problems.'
Prof Manore looked at supplements that fell into four categories: products such as chitosan (found in shellfish) that block absorption of fat or carbohydrates, stimulants such as caffeine that increase metabolism, products like conjugated linoleic acid that claim to change the body composition and appetite suppressants such as soluble fibres.
She found that many products had no randomised clinical trials examining their effectiveness, and most showed less than a two-pound weight loss benefit compared to the placebo groups.
She added that most research studies did not include exercise.
'I don't know how you eliminate exercise from the equation.
'The data is very strong that exercise is crucial to not only losing weight and preserving muscle mass, but keeping the weight off.'
A few products, including green tea and low-fat dairy supplements were found to have a modest weight loss benefit of 3-4 pounds but most of these supplements were tested as part of a reduced calorie diet.
'For most people, unless you alter your diet and get daily exercise, no supplement is going to have a big impact', Professor Manore said.
As a dietician and researcher, the professor said the key to weight loss is to eat whole grains, fruits, vegetables and lean meats, reduce calorie intake of high-fat foods, and to keep moving.
'Adding fibre, calcium, protein and drinking green tea can help,' she said.
'But none of these will have much effect unless you exercise and eat fruits and vegetables.'
The study is online in the International Journal of Sport Nutrition and Exercise Metabolism.