26 obese patients were recruited from primary care and enrolled in 10 week weight loss programmes. 14 had exercise on prescription sessions and minimal dietary advice and 12 had the same exercise regimen and intensive dietary monitoring using the UK Health of The Nation diet. They had weekly sessions with a team of final yeat BSc nutrition students. The group of 14 improved general fitness but did not loose weight whereas the group of 12 lost weight (mean value for group - 1.6 kg/m2) and showed an increase in thyroid function within the normal range.