The survey, commissioned by Herbalife, a maker of weight management foods, found that two thirds of respondents from the US, Germany, Italy, France and Russia claimed to be overweight but only 37 per cent believe they will still be overweight in five years time.
"People are not putting into practice what it really takes to lose weight. Many dieters are caught in a cycle of trying on various ad-hoc dieting approaches that have nothing to do with their specific needs - and they do so without making lasting changes," said Dr David Heber, founding director of the Center for Human Nutrition at the University of California, Los Angeles (UCLA), and chairman of Herbalife's Scientific Advisory Board.
"If they obtain results, they are quick and temporary. We know that right now, one-third of Americans are using a diet of their own creation - whatever that may be."
The survey confirms that the worldwide leader in obesity is still the US, "the catalyst in the growth of the worldwide waistline", according to Dr Heber. But Europeans are not far behind and despite a majority of those surveyed rating themselves as overweight, generally half of these believe they will be thin again in five years time.
For example, 70 per cent of German respondents described themselves as heavy but only 30 per cent think they will be heavy in five years. And only 37 per cent of Italians think they will be heavy in five years time, despite 67 per cent evaluating themselves as heavy. The French and Russians are less optimistic - 40 per cent of Russians think they will be heavy in five years time out of the 51 per cent who currently believe they are overweight.
But while both Americans and Europeans understand what makes people gain weight and which foods they should eat more of (fruits, vegetables) and less of (sweets, fats, oils), they may be at pains to decipher the wealth of information about diets.
"People with increasingly limited time are challenged to navigate an increasingly complicated food supply with a growing roster of covert `bad' foods - trans-fatty acids, hidden fats and sugars, and various `no-fat' foods that fuel appetite and hunger. So, against this backdrop, how is the average person, using a diet of his/her own creation, going to successfully cut 500-1000 calories a day in order to lose a pound of fat per week?" suggested Heber.
He notes that dieters tend to guess calorie contents and where calorie cuts should come from. But it is not necessarily any easier for individuals to select the right diet from those promoted by weight management companies.
A report published last year by Datamonitor revealed the extent to which consumer information on diets causes problems. Potential dieters are bombarded by a myriad of sources, including food manufacturers and retailers, and most effectively, the mass media. But this means that no clear message emerges, said the market analysts.
"The information is usually conflicting, and many less scrupulous publications are perfectly happy to report news of seemingly effortless and rapid diets and weight loss methods. Therefore, the majority of consumers are ill-informed about what they can realistically expect from dieting. This reflects poorly on the diet industry and is a major contributing factor to the ineffectiveness of people's dieting efforts," suggests the report.
It added that the food and drinks industry, as well as retailers, has the influence and financial leverage necessary to produce coherent information campaigns to educate dieters on nutritional matters.
"The message that dieters need to receive is that a diet alone is not a long-term solution to excessive weight. It is certainly part of it, but only within the context of a general pattern of healthy eating and exercise habits," said report author Lawrence Gould.
The ultimate aim should be that a person seeking permanent weight-loss is not consciously on a constant diet but rather has changed his or her lifestyle. Whereas a dieter may initially lose excess weight through a traditional diet, they should then be encouraged to move on to manufacturers' or retailers' other products which will help them to develop and maintain healthy eating patterns, he added.
Higher dieting success rates would in turn lead to a better image for the diet industry and higher confidence among consumers.