研究：每天一包薯片，一年后体重将增加约6.4公斤……
Daily bag of crisps could leave you a stone heavier

People drastically underestimate the number of calories in their snacks, with experts warning that eating a bag of crisps every day could lead to a stone of weight gain in a year.

A survey of around 2,000 adults found that around three quarters underestimated the impact of a small reduction could have. One in ten believed that cutting 200 calories a day would not affect weight.

When it came to snacks, people struggled, with 95 percent guessing that half a sharing bag of tortilla chips had 214 calories on average, almost half the true figure of 447.

He said, "Our environment has a real impact on what we eat, from adverts and supermarket promotions to what's available in our local corner shop.

"If we had fewer cues to snack, or were pushed to buy fewer high calorie snacks, we should be able to see real change."

New rules coming into force in October will restrict promotions on foods high in fat, sugar and salt in big shops.

Body mass index (BMI) is a simple index of weight-for-height that is commonly used to classify overweight and obesity in adults. It is defined as a person's weight in kilograms divided by the square of his height in meters (kg/m²).