SACN report on energy requirements
The figures for the average amount of energy (MJ, kcal) people in the UK population need per day were last estimated in 1991 by the Committee on the Medical Aspects of Food and Nutrition Policy (COMA). The science of estimating energy requirements has moved on since this previous report and the Scientific Advisory Committee on Nutrition (SACN) has today published its final report on energy requirements in the UK population.
This involved looking in depth at how to calculate the energy required for our basic body functions – the basal metabolic rate (BMR), and also the amount of energy used on average by physical activity. The committee reviewed current evidence on the energy requirements of different population groups. Although the report shows that previous estimates for energy requirements of specific age groups now need some adjustment (upwards for adolescents and adults), this does not indicate that as a population we should be eating more. The new values are simply a closer approximation of energy needs at current activity levels, estimated using updated methodology.
The majority of adults in the UK are overweight or obese (over 60%) and so there is a need for many to reduce their energy intakes in order to achieve a healthy weight. Therefore, SACN has established energy intakes associated with a healthy bodyweight. People who have higher body weights will correspondingly have greater energy requirements to maintain this excess weight and so consuming fewer calories will help them to move towards a healthier body weight.
- The new energy requirements published are a result of a scientific review of evidence on energy requirements and methods of estimating the average number of calories needed by different population groups per day.
- Although in many cases the estimated requirements have increased, this does not mean that the population should be consuming more energy.
- Because most adults in the population are already overweight or obese, SACN has specifically provided energy intake values that are consistent with a healthy weight. These will help people who are above (or below) this level to move towards a healthy weight.
- Guideline Daily Amount (GDA) values used for food labels are part of European labelling regulations and so the calorie GDA values of 2000 calories per day for women and 2500 calories per day for men will still be used on food labels. In any case these values are broadly in line with the revised estimates for average energy requirements for adults of 8.7MJ/d (2079kcal/d) for women and 10.9MJ/d (2605kcal/d) for men.
- For older adults who are no longer mobile, their activity levels and so their energy requirements may be lower, and alternative energy intake values for lower levels of activity have also been estimated.
- Many women begin pregnancy already overweight, but weight loss during pregnancy may be harmful to the developing child. Given this uncertainty, SACN has recommended that the energy requirements during pregnancy should be based on the woman’s pre-pregnancy bodyweight rather than the requirements for a healthy weight for non-pregnant women (i.e. a bodyweight in the BMI range 18.5-24.9kg/m2). As previously recommended, an additional 0.8MJ (about 200kcal) per day is needed during the last 3 months of pregnancy. For women who are breastfeeding, an additional 1.38MJ (330kcal) per day is needed in the first 6 months of lactation.
- New reference values for children of different ages have also been published
In its report on energy intakes, SACN also concludes that there is consistent evidence that physical activity is associated with reductions in the risk of chronic diseases such as coronary heart disease, stroke and type 2 diabetes, and the risk of preventable death. It may also reduce the risk of becoming obese provided energy expenditure is greater than energy intake.
Obesity call for action
As part of the government’s Public Health White Paper, published in November 2010, it was highlighted that action would be needed to address the obesity epidemic in the UK.
In order to reduce the prevalence of overweight and obesity in the population, energy balance needs to be shifted so that those who are overweight or obese burn off more energy than they consume and so lose weight over time. This negative energy balance can be induced by reducing energy consumed (consuming fewer calories), increasing energy expended (increasing physical activity) or both.
In practical terms, most people will need to reduce their energy intake to lose weight as it can be difficult to do enough physical activity to cause weight loss. However, being physically active alongside a controlled diet can help preserve muscle mass when losing weight and also has many other health benefits.
The government’s call for action focuses on the need to reduce calorie intake and emphasises that we all have a part to play. In particular it calls for a reduction in the calorie content of the food supply and for the food industry to reduce the number of calories provided by their products.
This follows on from work by a group of scientific experts, which suggested that a reduction in daily calorie intake across the population of 100kcal per day could help slow the increase in the prevalence of obesity. A stakeholder meeting was also held earlier this year to discuss how the food industry could reduce the number of calories provided by their products