It only takes a few hundred extra calories eaten here and there to trigger weight gain.

And for every extra 24 calories eaten during a meal, the risk of becoming overweight rockets by nine per cent.

But as body size increases, whales get less caloric bang for their buck when hunting, meaning the ratio of calories eaten to calories burned declines.

It will even calculate calories eaten and burnt.

Three cereals rice, wheat, and maize (corn) provide more than half of all calories eaten by humans.