Obese older adults can reduce their chances of developing the metabolic syndrome which raises the risk of diabetes and heart disease by adding exercise to a diet regime, research shows.

The study followed 107 obese adults aged 65 and older for one year and randomised them to four groups – weight management with a calorie-restricted diet, three 90-minute exercise sessions a week without dieting, combined dieting with exercise, and controls (no diet or exercise.)

The combination of diet and exercise nearly doubled the improvement in insulin sensitivity compared with dieting alone. The insulin sensitivity index did not improve in controls but improved by 40 per cent in the diet group and by 70 per cent in the combined diet-exercise group.

Even moderate weight loss can significantly reduce levels of circulating oestrogens which are associated with an increased risk of breast cancer, US researchers have found.

Results suggested that losing just five per cent or more of one's weight could cut by a quarter to a half the risk for the most common, oestrogen-sensitive breast cancer said researcher, director of the Prevention Centre at Fred Hutchinson Cancer Research Centre, Dr Anne McTiernan.

The study in 439 overweight to obese sedentary women aged 50 to 75 was the first to show that losing weight through a healthy diet significantly lowered blood oestrogen levels in postmenopausal women and led to average weight losses of 10 percent of their starting weight. The most striking effect was if diet was combined with exercise.

"This shows that it's never too late to make lifestyle changes to reduce your risk for breast cancer," Dr McTiernan said.