The best way for a woman to lose weight may be to eat like her Stone Age ancestors.
New research shows a cavewoman diet is potentially one of the most effective ways to slim.
Scientists came up with the findings after tracking female dieters for up to two years and comparing weight loss among those on the cavewoman - or paleolithic - diet with those complying with modern nutritional guidelines.
Results show women who ate like their predecessors lost twice as much body fat in the first six months as those on the modern-day diet.
They also saw their waistlines shrink by a greater amount and levels of harmful blood fats called triglycerides decline more sharply.
Interest in paleolithic eating habits first arose a few years ago when scientists at the Karolinska Institute in Stockholm, Sweden discovered eating like a caveman for just three weeks slashed the risk of heart attacks and strokes in men.
A paleolithic diet usually centres around berries, vegetables and lean meat but forbids foods such as cereals, beans, dairy products and pasta.
In the latest study, scientists from the Medical Research Council Epidemiology Unit at Cambridge University teamed up with colleagues at Umea University in Sweden to track obese women over a two-year period.
They recruited 70 heavily overweight women and split them into two groups.
One was assigned to a diet based around paleolithic foods and the other to a Scandinavian-type diet based on something called Nordic Nutrition Recommendations.
These recommendations are updated every few years and revolve around a diet based mainly on whole-grain cereals, low-fat dairy goods, fruit, pulses, fish and vegetable oils.
After six months, those on the cavewoman diet had lost an average of 6.2 kilogrammes of fat and saw an 11-centimetre reduction in waist circumference.
Women on the Nordic diet lost only 2.6kg of fat and their waist circumference decreased by just 5.8cm.
Levels of triglyceride, a type of fat in the blood associated with increased heart disease risk, also dropped significantly in the Stone Age diet women but not those on the Scandinavian regime.
Blood pressure and cholesterol level were similar between the two groups.
By the end of the two-year study, there was much less of a difference between the two groups, suggesting weight loss slowed in those on the Stone Age diet.
Although the research focused on postmenopausal women, it's expected that younger women and men of all ages would benefit in the same way.
In a report on their findings, published in the European Journal of Clinical Nutrition, the researchers said: 'A paleolithic diet has greater beneficial effects than a Nordic diet regarding fat mass, abdominal obesity and triglyceride levels in obese postmenopausal women.'
Catherine Collins, chief dietician at St Georges Hospital in London said the Stone Age diet appeared to accelerate weight loss in the first six months.
But she stressed women appeared to lose less fat as the study progressed.
'This may be because the paleolithic diet is very low in protein, lacking in meat, eggs, cheese and milk. One of the effects of that is to slow the body's metabolic rate (the rate at which it burns calories).
'As the metabolic rate declines, at some point that will stop you losing weight.'