A) Along with old classics like "carrots give you night vision" and "Santa doesn't bring toys to misbehaving children", one of the most well-worn phrases of tired parents everywhere is that breakfast is the most important meal of the day. Many of us grow up believing that skipping breakfast is a serious mistake, even if only two thirds of adults in the UK eat breakfast regularly, according to the British Dietetic Association, and around three-quarters of Americans.B) "The body uses a lot of energy stores for growth and repair through the night," explains diet specialist Sarah Elder. "Eating a balanced breakfast helps to up our energy, as well as make up for protein and calcium used throughout the night." But there's widespread disagreement over whether breakfast should keep its top spot in the hierarchy (等级) of meals. There have been concerns around the sugar content of cereal and the food industry's involvement in pro-breakfast research -- and even one claim from an academic that breakfast is "dangerous".C) What's the reality? Is breakfast a necessary start to the day or a marketing tactic by cereal companies? The most researched aspect of breakfast(and breakfast-skipping) has been its links to obesity. Scientists have different theories as to why there's a relationship between the two. In one US study that analysed the health data of 50,000 people over seven years, researchers found that those who made breakfast the largest meal of the day were more likely to have a lower body mass index (BMI) than those who ate a large lunch or dinner. The researchers argued that breakfast helps reduce daily calorie intake and improve the quality of our diet -- since breakfast foods are often higher in fibre and nutrients.D) But as with any study of this kind, it was unclear if that was the cause -- or if breakfast-skippers were just more likely to be overweight to begin with. To find out, researchers designed a study in which 52 obese women took part in a 12-week weight loss programme. All had the same number of calories over the day, but half had breakfast, while the other half did not. What they found was that it wasn't breakfast itself that caused the participants to lose weight: it was changing their normal routine.E) If breakfast alone isn't a guarantee of weight loss, why is there a link between obesity and breakfast-skipping? Alexandra Johnstone, professor of appetite research at the University of Aberdeen, argues that it may simply be because breakfast-skippers have been found to be less knowledgeable about nutrition and health. "There are a lot of studies on the relationship between breakfast eating and possible health outcomes, but this may be because those who eat breakfast choose to habitually have health-enhancing behaviours such as regular exercise and not smoking," she says.F) A 2016 review of 10 studies looking into the relationship between breakfast and weight management concluded there is "limited evidence" supporting or refuting (反驳) the argument that breakfast influences weight or food intake, and more evidence is required before breakfast recommendations can be used to help prevent obesity.