It has been revealed that fast food manufacturers and food caters are allocated a 20 percent margin of error when it comes to listing the calories in the food they make and sell.

This means that a meal listed as 500 calories may in fact contain 20 percent more calories than suggested, or in this case an extra 100 calories. That means the 500 calorie listed food contains 600 calories.

Research from Tufts University, Boston, USA highlight that the food manufacturing sector seems to work at the upper end of this margin of error. Research of 29 restaurant dishes found in restaurants suggested that they contained on average 18 per cent more calories than listed in menus, with seven restaurants of the 29 having a whopping 50 per cent more calories than consumers believed.

What does this means in terms of weight management? Well, 1 lb of body fat contains 3,500 calories. So, it would only take 35 meals that suggest one thing but contain an extra 100 calories to start seeing weight gain.