Celebrity diets often have little science to support their claims, according to an Irish nutritionist who is taking part in a major science conference in Dublin this week.
As well as leading only to short-term weight loss, many of the diets are unhealthy, Dr Claire MacEvilly from the British Medical Research Council believes.
Dr MacEvilly is attending the British Association's annual Festival of Science which is being held in Dublin this week for the first time since 1957. Hundreds of talks, presentations and events are scheduled for the week.
Dr MacEvilly, who is originally from Dublin, says that popular diets such as the Atkins diet, in which carbohydrates are excluded, only work because people eat fewer calories, rather than because of the change in the diet composition. "The Atkins diet encourages people to eat more meat, which essentially means eating more saturated fat, and to exclude all fruit and vegetables," she explains.
"However, we know that people who eat more fruit and vegetables are more healthy and get all their essential vitamins and minerals."
The GI diet, which has become popular recently, suggests switching to more wholegrain foods in order to decrease hunger and promote weight loss. "While there are benefits of eating wholegrain foods, science doesn't currently support the weight loss claims that are made," says Dr MacEvilly.
"There is the continual promotion of random celebrity diets," she says. "Common to them all is the promise of quick weight loss on the basis of changing meal plans or excluding particular food groups."
These dramatic changes in eating habits can be difficult to maintain, she says. "Research has shown that less than half of all people starting a diet are still adhering to the diet one year later.
"These diets turn food into a big issue and people get obsessive about it. It has to be a long-term lifestyle decision, not a quick fix solution."