Having a married affair may be one of the most effective way to shed the pounds, a bizarre survey has found.

Just over half of men and 62 percent of women said they had shed pounds after embarking on an affair.

Philandering men lost an average of 6lbs whilst the women claim to have lost 10lbs on average.

Although the survey, which was carried out by a dating website for married people seeking affairs, should clearly be taken with huge pinch of salt, experts say that there are several physiological reasons why being unfaithful might aid weight loss.

Craig Jackson, Professor of Psychology at Birmingham City University, told MailOnline: ‘Engaging in an affair puts an enormous amount of pressure on an individual.

‘Telling lies, avoiding direct confrontations and sneaking around someone’s back cause a lot of stress.

‘Being stressed has a whole range of effects on your body. You produce adrenaline and the stress hormone cortisol, your heart rate goes up, your breathe faster, your blood pressure rises and levels of serotonin are increased. All this can burn calories.

‘There are also the behavioural changes that take place when you have an affair.

‘When you’re up to no good, you’re more likely to be rushing from A to B, with less time to eat your lunch or have that extra pint. These things can also effect weight loss.

‘Furthermore, there is a physical pressure.

‘Many men will want to be the alpha male, and looking good for their new lover is important.’

Both physical and behavioural factors may lead to weight loss as the result of an affair

‘Also the chances are, if you’ve been married for 20 years, you’re probably not having sex that often  [and benefiting from the calorie burn that brings].’

It’s estimated that having sex can burn anything between 100-300 calories per 30 minute session.

A spokesperson for the dating website, UndercoverLovers.com, which carried out the survey on 3,000 of its adulterous members, said: ‘Having an affair can provide a huge psychological fillip.

‘It’s well known that we eat more, and less healthily, when we’re unhappy.’

But adulterous men beware: While it’s well-known that regular sex can be good for the heart, researchers at the University of Florence have discovered that married men who cheat on their partners increase their risk of a heart attack.

One reason may be that men who embark on extra-marital affairs may have an unhappy home life, and depression has been linked to an increased risk of heart disease.

Conversely, being in a happy relationship seems to protect men from cardiovascular events, they found.