Monday November 16 2009
“You can eat an extra cheeseburger a day,” according to the Daily Mail, which reported that the official guidelines on recommended calorie intakes have been lower than they should have been for the past two decades. The newspaper said that the average adult could “happily squeeze in an extra 400 calories a day”.
The news is based on a draft report by an advisory committee to the government. It found that the original recommendations for daily energy (calorie) intakes, which were made in 1991, underestimated the average requirement by up to 16%. This discovery came about through a re-evaluation of the amount of energy needed by the average person based on what the authors consider a more accurate interpretation of average physical activity levels.
This news does not mean that everyone can, or should, now eat an extra cheeseburger or its equivalent in calories a day. The advisory committee makes it clear that the revised energy intake recommendations do not mean that people should increase the amount they eat and that, if people do eat more, they will need to do more exercise to avoid being overweight or obese.
What is the basis for the news reports?
The news is based on a draft report from the Scientific Advisory Committee on Nutrition (SACN), a committee of independent experts that advises the Food Standards Agency and Department of Health, as well as other government agencies and departments.
The main point of the SACN report is that the existing recommended calorie intake appears to be too low for adults, and may be increased by up to 16%.
What did the report conclude?
The 250-page report highlights the findings and recommendations of the SACN Energy Requirements Working Group. Its purpose was to review and agree the methods and assumptions that are used to define energy requirements, to decide how to determine requirements for the UK population, and to agree dietary reference values (recommended intakes) that take into account age, body size, activity levels, gender and physiological state (pregnancy, growth etc).
The report discusses the theory behind dietary intakes of energy, physical activity and energy expenditure levels, population energy requirements, the effect of diet on the risk of weight gain and the effects of physical activity.
The draft report's main conclusions are:
- SACN has determined new estimated average requirements (EARs) for energy for children, adolescents and adults. This is based on an improved understanding of physical activity levels. For teenage boys from 15, girls from 11 and for all adults, EAR values should be increased by up to 16% (based on an increased average physical activity level, or PAL, of 1.63, see below). Values have been established for three physical activity levels (average, less active and more active) in each age group and gender. The report says that for those people judged to be either less or more active than average, PAL values of 1.49 and 1.78 are appropriate. They say that energy requirements may be slightly lower for less active individuals and active individuals may have higher energy requirements.
- Revised reference values do not mean that individuals or groups should increase their energy intake. Energy expenditure (the amount of energy that people use up) needs to increase in relation to energy intake from food to reduce the number of overweight and obese people.
- SACN fully endorses the current recommendations on physical activity, which state that adults should do at least 30 minutes of moderate-intensity activity five or more days a week, while children and teenagers should aim for 60 minutes a day.
What are the existing calorie intake guidelines?
Current guidance is based on the recommendations of the UK Committee on Medical Aspects of Food Policy (COMA), which were made in 1991. This guidance has since been adapted to include recommendations for fibre intake by the Food Standards Agency and for salt intake by SACN.
The current UK guideline daily amounts are 2,000 calories for women, 2,500 calories for men and 1,800 calories for children aged five to 10.
Why is the original guidance thought to be wrong?
The researchers say that the recommendations made by COMA in 1991 were based on a potentially less accurate methodology, which included assumptions that individuals’ physical activity levels could be predicted from activity diaries and lifestyle questionnaires. They say that this method underestimated the influence of routine activities of daily living on energy expenditure.
For their estimates of physical activity levels, the researchers carried out a search of the literature for studies that assessed total energy expenditure in a particular way. They looked at a range of basal metabolic rates (the energy a person expends when resting), total energy expenditures and other measurements (e.g. growth), which they used to determine the physical activity levels of the UK population for a range of ages. The calculations are complex, but the authors say that while there are limitations to the way they derived physical activity levels for the different age groups, their approach is evidence based and more accurate than the one previously used.
Much of the report is dedicated to justifying the need for improved methodology to determine energy recommendations for adults and children in the UK.
The authors say that the COMA group estimated the average physical activity level in the UK to be 1.4. The measure of physical activity (PAL) is described as being an index of 24 hour total energy expenditure (TEE), adjusted for the basal metabolic rate (BMR), i.e. it is a ratio of TEE to BMR. The authors say that this is a relatively low value but, at the time, was “seen to be in keeping with the sedentary lifestyle of the UK population”. However, according to their own calculations, this estimate is likely to be lower than the true average physical activity of the UK population (90% of the subjects considered relevant for this report had physical activity levels greater than this value). Their estimate for the average physical activity level for adults is 1.63.
Using this value, the researchers estimated the average energy requirements for adults to be up to 16% higher than the original recommendations.
Can you really eat an extra cheeseburger a day?
This news does not mean that everyone can, or should, now eat an extra cheeseburger or its equivalent in calories a day. The conclusions of this report should not be oversimplified. People who are overweight are still likely to be consuming more energy (i.e. food) than they are burning (using up). The researchers state in their report:
“The high prevalence of overweight and obesity in the UK population shows that, for the majority of people, energy intakes are in excess of energy requirements. It is important that the proposed EAR values are not used to signal or encourage an increase in energy intake of the population as a whole; this would increase the prevalence and magnitude of overweight and obesity in the absence of a corresponding increase in energy expenditure.”
What happens now?
This draft report by SACN has now entered a consultation period. Its findings and recommendations will need peer review and further consideration by experts before they are incorporated into national guidance. The consultation period will run until February 11 2010, after which time the feedback and subsequent review will be made available to the public.
An announcement on the SACN website says that estimating energy requirements is complex and the new draft recommendations are themselves based on assumptions.
If the government adopts the new recommendations, they will have implications for the health and food industries. For example, food labelling is based on the current recommended daily allowances.