Metabolic fuel utilisation in obese women before and after weight loss.

OBJECTIVE

To test the hypothesis that weight rebound following slimming diets may be caused by an adaptive alteration in fuel utilisation involving a suppression of fat oxidation thus favouring fat storage in adipose tissue.

DESIGN

Repeat measurements before and after two 14 d cycles of controlled weight loss using a very low energy diet (1.9MJ/d).

SUBJECTS

Eight moderately obese women (body weight: 85.6 +/- 10.1 kg, BMI: 31 +/- 2 kg/m2, age: 42.6 +/- 10.1 years).

MEASUREMENTS

Energy expenditure and substrate balances using 24-h whole-body indirect calorimetry and naturally labelled 13C-glucose.

RESULTS

Aggregate weight loss was 5.1 +/- 0.8 kg. Twenty-four hour energy expenditure declined by 12% (8359 +/- 282 to 7366 +/- 191 kJ/d, p < 0.001). Net fat utilisation was not significantly depressed (4009 +/- 366) to 3613 +/- 191 kJ/d, NS), and the proportion of energy derived from fat was unchanged at 48.0% before weight loss and 49.0% after weight loss.

CONCLUSION

The well-recognised phenomenon of reduced energy expenditure is unlikely to be a major cause of weight regain. The results do not support the theory that altered fuel selection in post-obese subjects may be the cause of difficulty in maintaining weight loss.