The severely obese are likely to face a ‘fat tax’ when renewing life insurance polices, a leading insurer has revealed.

Legal and General has said that it will use the Body Mass Index to determine who should pay higher premiums.

Those who are overweight face a hike of 50 per cent, with high risk applicants who have medical problems or who smoke facing a fourfold rise.

“Most people understand that poor diet and lack of exercise can lead to health problems but they might not realise that being significantly overweight would also make their life insurance more expensive,” said L&G’s Russ Whitworth.

“Although it is not an exact science, we find that BMI is the best indicator of the risk of being overweight, so it pays to stay in shape.”

Anyone with a BMI of over 30 is considered obese, and other insurers have also revealed that they charge extra if people fall into this category.

“If you are obese, you are at greater risk of contracting certain diseases,” said an Association of British Insurers spokesman. “It is just the same as increasing the premium for a smoker or somebody with previous medical conditions.”