Australian researchers say they've discovered a drug that has the potential to prevent obesity in children born to overweight mums.

There's evidence that maternal obesity can increase a child's risk of obesity later in life.

A new study on rats at the University of NSW has shown a drug called NMN can reduce this risk by increasing energy metabolism of the offspring.

"Our study offers some promise that we may have another approach that might be appropriate to prevent obesity in children from overweight mothers," said lead author Professor Margaret Morris - Head of Pharmacology in the School of Medical Sciences at UNSW.

However, the expert said that in no way does this advocate against the benefits of exercise and good nutrition.

"Exercise is still best," Prof Morris said.

"We also found that exercise can reverse most of the negative consequences of maternal obesity," she said. "But we know that exercise for some people it is difficult. Some people cannot fit it in their day, and some people cannot exercise for various reasons.

"So there is probably some interest in trying to moderate these metabolic effects using other means."

To investigate the impact of NMN, researchers studied baby rats born to obese mothers and lean fathers.

One group of offspring were treated with daily exercise on a treadmill for nine weeks, while another group received a daily injection of drug NMN for three weeks.

The findings, published in journal Scientific Reports, found both interventions reduced fat levels in the blood and also modest improvement in glucose tolerance.

"NMN appeared to have stronger effects on liver fat catabolism and synthesis (Fasn) than exercise," the authors wrote.

"This work encourages further study to confirm the suitability of NMN for use in reversing metabolic dysfunction linked to programming by maternal obesity," they concluded.

Prof Morris said it's thought the drug works by promoting an enzyme known as NAD (Nicotinamide adenine dinucleotide), the same way exercise does.

This, she said, boosts metabolism by improving the efficiency of the mitochondria - the energy powerhouses in all living cells.

"We know that obesity tends to reduce the levels of NAD so we are trying to give the tissues back something that is helpful for metabolism," Prof Morris said.

"However, we do still need to look at other effects of the drug. For instance, we need to make sure it has no toxic effects, which we are following up in other studies."

- AAP