Hello. I am a professor of nutrition and dietetics at King's College, London. I have over 30 years' experience working in nutrition science.
My observation on childhood obesity is that the epidemic has occurred in the United Kingdom and other countries despite any changes in the relative proportions of fat or sugar in diets. The evidence from weighed food intake surveys tends to indicate that total food energy has fallen by between 20% or 30% over the past 30 or 40 years, yet the increase in obesity has gone up.
One of the fundamental questions is whether the relative proportions of fats and carbohydrates in diets are important or whether it's total energy intake. I would put to you that the major determinant is the food energy intake, regardless of whether it's primarily from fats or carbohydrates. In support of that, I would point to the results of some recent randomized controls trials. One of the longest ones was carried out in a women's health initiative that basically showed that if you gave advice to get people to reduce the proportion of their food energy derived from fat, it didn't really lead to any long-term changes in weight.
I would argue that the focus in terms of diet should be on matching calorie intake with energy expenditure. It is quite clear that energy expenditure has fallen, but the fall in calorie intake hasn't been sufficient to match the drop in energy expenditure.
One of the issues that has occurred in the U.K. is actually how to inform consumers best to change their dietary habits so that they can avoid obesity—and particularly, the focus on children.
There are two areas that I think deserve consideration. One is the way in which the information is put across, whether it's put across as numerical information or as qualitative information, high, medium, or low, or whether it's a colour-coded system, such as traffic lights, red, amber, and green.
I don't really want to spend any time talking about the methods of display, which I think will vary between cultures, but I want to spend a little bit of time on the way in which you derive what is high, medium, or low that might be used potentially for a regulatory instrument to restrict advertising or to give consumers advice.
The U.K. Food Standards Agency has come out in favour of a traffic light system based on the grams per hundred grams of food for labelling. It has used, as the basis for its labelling, fat, sugar, salt, and saturated fat. Unfortunately, it has not used calories in that labelling.
The major problem of using nutrient composition per hundred grams is that it does not tell you the amount of food consumed, so you label a food as being high for a small portion as well as a large portion. Portion size, I believe, is a major driving factor for obesity. It has become quite clear that portion sizes have been increasing, particularly in the last ten years. You can just think of it as regards cups of coffee or carbonated beverages. They get bigger every year.
The alternative way of expressing dietary intake is relative to a benchmark, and the benchmark that has been most widely used is the guideline dietary amount. The guideline dietary amount is an arbitrary benchmark that can be used to give you an idea of the amount of calories an individual requires and then a proportion of the calories provided by the food.
I think guideline dietary amounts for the appropriate groups are the way in which to base food labelling, rather than on the amount per hundred grams. There are instances where the amounts per hundred grams as a labelling basis being used by the Food Standards Agency become particularly confusing. For example, if you take a food like mustard, mustard would be labelled as red, as high, because it has a high fat content, but you wouldn't consume 100 grams of mustard. Similarly, you need to be aware that certain foods that you need to encourage children to consume in moderation—for example, cheese—would be labelled in an adverse manner by expressing it as an amount per hundred grams.
So in conclusion, I think if you're considering a format of food labelling, I would strongly advise that you go for the amount provided in a portion, and I would focus on really just one thing: food calories. I don't believe the evidence is there to show that the proportion of calories from sugar or fat is particularly useful. It's the total calorie intake that's most useful.
That's all I have to say.