In a 2011 study, for instance, people who drank the same 380-calorie(卡路里) milkshake on two separate occasions produced different levels of hunger-related hormones (荷爾蒙), depending on whether the shake's label said it contained 620 or 140 calories.

Hunger levels depend on one's consumption of calories

People tend to take in a lot more calories than necessary.

Choose food with fewer calories

So why not limit the density of food outlets, particularly ones that sell food rich in empty calories?

Among other requirements, they must offer a side dish that meets similar criteria, with fewer than 200 calories and less than 35%of its calories from sugar.

Energy Usage: Energy is an essential resource across the entire food production cycle, with estimates showing an average of 7-10 calories of input being required in the production of one calorie of food.

This varies dramatically depending on crop, from three calories for plant crops to 35 calories in the production of beef.

Some iced coffees have as many calories as a hot dinner.

Better skip dinner or hit the gym afterwards, with a cancer charity warning that some iced coffees contain as many calories as a hot dinner

The World Cancer Research Fund (WCRF) conducted a survey of iced coffees sold by some popular chains in Britain including Starbucks, Caffe Nero and Costa Coffee to gauge the calories as studies increasingly link obesity with cancer.

The worst offender - a coffee from Starbucks -- had 561 calories

Other iced coffees contained more than 450 calories and the majority had an excess of 200.

Health experts advise that the average woman should consume about 2,000 calories a day and a man about 2,500 calories to maintain a healthy weight.

Dieters aim for 1,000 to 1,500 calories a day

The fact that there is an iced coffee on the market with over a quarter of a woman's daily calories allowance is alarming," Dr Rachel Thompson, science programme manager at London-based WCRF, said in a widely-reported statement.

This is the amount of calories you might expect to have in an evening meal, not in a drink