People who reward themselves after a fitness training session by munching a large meal may end up consuming more calories than they managed to burn off in the first place.

It is a common misconception that an hour spent exercising justifies eating a greasy burger or plate of chips, Jeni Pearce, performance nutritionist at the English Institute of Sport, tells the Independent.

In fact, a typical exercise session burns only 200 to 300 calories - which is easily replaced with one sugar-loaded sports drink.

"People may think they've expended 500 calories because they've worked really hard for an hour," Ms Pearce said.

"But the reality is they may have only burned 250 to 300 calories."

One reason for this discrepancy, says Ms Pearce, is the difficulty in accurately measuring calorie expenditure: the fitter a person gets, the harder they can work during a gym session, hence the more calories they are able to burn.

However for those who want to lose weight - and keep it off - the key thing is consistency.

To reduce body fat takes time and is more difficult than most people realise, Ms Pearce notes, adding "you have to be in it for the long haul".

Experts recommend that those struggling to stick to a healthy eating plan should set realistic goals to keep in mind why they want to lose weight in the first place.

Nutritionist Shereen Jegtvig advises that people hoping to shed a few pounds are more successful if they monitor the types of food they consume and their calorie intake by keeping a 'food diary' and writing down what they eat each day.

"Keeping track of your diet will help keep you motivated and give you a realistic idea of how much healthy food versus how much unhealthy food you are eating," says Ms Jegtvig.