Researchers in Britain say that obese people can become healthier without losing weight.
The researchers from Leeds Metropolitan University and the University of Hull, say women who are clinically obese don't need to diet to improve their health, they just need to become more active.
The team produced a programme which encouraged women not to diet but to take part in exercise classes and also taught them about good eating habits, such as how to cook, and they also provided them with social support.
The researchers found within a year all the women showed significant improvements in health and mental well-being and although they had only lost a little weight they were significantly fitter and happier with themselves.
The team say a healthy lifestyle can improve health risks regardless of weight.
For the study 62 women aged 24 to 55 years, all with a Body Mass Index (BMI) of over 30, which is classed as clinically obese, took part in four hours a week of exercise, such as Tai Chi, aqua aerobics or circuit classes.
The programme also included educational sessions to teach them how to read food labels and cook food, and behavioural therapy to help the women respond to body cues such as hunger and feeling full.
One of the exercises used by the dietician encouraged the participants to eat a chocolate bar in small portions over the course of a week.
The women were encouraged not to diet and to eat whatever they wanted in moderation.
Even though the women only lost a small amount of weight, they were significantly fitter and blood pressure, heart rate and cholesterol fell and respiratory fitness improved.
The women also felt better in terms of general well-being, body image, self-perception and stress.