A Senate estimates committee has heard large numbers of Defence Force personnel are overweight or obese, and almost 10 per cent are not deployable on medical grounds.

The Vice Chief of the Defence Force, Lieutenant General David Hurley, listed the latest figures as based on body mass index (BMI).

The figures show about half of all regular male Defence personnel are classed as overweight and well over 10 per cent are obese.

In the Army 14 per cent of males and 7 per cent of females were classed as obese, while 49 per cent of males and 30 per cent of females were overweight.

Seventeen per cent of males and 8 per cent of females in the Air Force were obese, while 53 per cent of males and 37 per cent of females were overweight.

While in the Navy 15 per cent of males and 11 per cent of females were obese, and 57 per cent of males and 28 per cent of females were overweight.

Liberal Senator Guy Barnett told Lieutenant General Hurley the problem appears to be worsening.

But Lieutenant General Hurley said BMI is not an effective indicator of deployability.

"BMI does not indicate deployability. For example, I'm 180 centimetres, 95 kilos. I'm 29.7 on the BMI scale which makes me extremely overweight, close to obese, but I'm extremely deployable," he said.

He also emphasised the increase in non-deployable troops, from 8.3 per cent in 2009 to 9.7 per cent, was not solely due to obesity.

"We've got a lot of people coming back from operations who may have moved from a fit state while they are away to an unfit state," he said.

"So this could be quite unique factors at play or it could be a cyclical issue... but I would not link that increase directly with obesity."

And he rejected suggestions the Defence Force needed outside help to address the problem of obesity.

"We are heavily engaged with the Royal Australian College of General Practitioners, the General Practitioners Network, the Centre for Military and Veterans Health... we tap into a wide range of expertise in these areas," he said.