During National Science and Engineering Week, Dr Susan Jebb, Head of Diet and Population Health at the Medical Research Council Human Nutrition Research Unit (HNR) gave the annual IFR in the City Lecture.

Her talk, ‘Food for a leaner future’ touched on the science underpinning nutrition, from basic fundamental aspects through to social sciences, but focussed on what we know about eating healthily and how we can enable people to make the better choices. Dr Jebb suggested the question should be not why so many are over weight, but how those who are an appropriate weight remain healthy in a modern society where we rarely even get out of breath and high-fat-high-sugar foods widely accessible.

Dr Susan Jebb

We have an ancient physiology, moulded by famine, which is ill equipped for modern life. The difference between maintaining a healthy weight and becoming obese can be as little 20-30 calories extra per day. This discrepancy means over a quarter of UK adults are currently overweight as well as 14% primary-aged and 20% secondary school children, and more children and adults in northern England and Scotland are more overweight than those in the south-east.

Carrying excess fat (typically 30-40Kg) places considerable physiological stress on the human body, which leads to the development of diabetes and increases an individual’s risk of cardiovascular disease (i.e. heart attack and stroke) and range of cancers (e.g. bowel and breast). The cost to the NHS is currently £4.2Bn, but it is estimated to rise to £50Bn in the next 10 years. However, the cost is far greater in terms of the burden on individuals and the wider economy through ill health.

Studies have shown that even small changes can make a significant difference, For example, if the UK population followed the advice provided by Five-a-Day eating more fruits and vegetables, reducing salt, sugar and saturated fat, there would be 70,000 fewer deaths annually. The science behind healthy eating is relatively easy; the problem is getting people to change their behaviour and establishing who is responsible for achieving sustainable change, e.g. individual, parents, schools, health professionals, food industry or government.

Dr Jebb described some options for reducing weight including bariatric surgery (i.e. gastric bypass and banding), which is effective for weight loss (20-30 Kg), but only suitable for those who are morbid obese. Currently, only one drug is licensed for weight-management; orlistat works by blocking fat absorption and is available on prescription or over-the-counter, but its success it modest.

Change in diet and physical activity is cheap, low risk and highly effective alternative. Such lifestyle changes are hard to achieve and maintain, but even small differences can prevent long-term ill health For example, the US Diabetes Prevention Program showed obese volunteers who lost 7 Kg following intensive diet and health support reduced their risk of diabetes by 58% despite regaining 3 Kg in the following four years. Similar benefits were also noted in patients referred to WeightWatchers™ by their GP.

A more sustainable alternative may be to avoid weight gain. However, most advice focuses on hard-core nutrition (e.g. eat more fish) not diet and lifestyle choices (e.g. eat breakfast). F.A.T. encourages individuals to think about what they are eating in terms of frequency (F), amount (A) and the types of foods (T).

When once eating and drinking in the street would be deemed socially unacceptable, we think nothing of grabbing food (grazing) whilst travelling, sitting at our desks or in front of the television. This behaviour means we rarely feel full or hungry, encouraging over-consumption. However, it is not just what we eat, but also how much. Portion size is distorted by packaging, cost and availability. A single bar of chocolate may contain the same calories as a meal, and we have bought into the idea that if we eat something now (ca. 20% recommended daily intake), we will eat less at the next meal, which is simply not true. Larger packets encourage greater consumption: given a larger packet, we cook more and eat more and for every 600 calories extra served, we consume an additional 160 calories. This obesogenic behaviour is important in understanding why people gain weight, but major risk factors for obesity also include not eating some foods (e.g. fruits and vegetables) and consumption of soft drinks, which increase intake without impacting satiety.

To prevent weight gain need to change our environment, our behaviour and the food product available. But, how far are we prepared to go as individuals or society has yet to be explored fully. Dr Jebb described some of the options on the Nuffield Ladder of Intervention from doing nothing to eliminating choice.

Monitoring and surveillance (e.g. national diet and nutrition survey) has show the population is getting fatter whilst access to diet and lifestyle choice is widespread. However, the decisions we make about our food are not conscious and logical. Thus, nudging, unconsciously persuading individuals to adopt healthy choices through socially acceptable norms may be one option. Others may be to reduce the availability of high-fat, high-sugar foods, reformulate food products to contain fewer calories or increase satiety, or offer incentives for the right choice. Disincentives (e.g. higher taxes on unhealthy foods) are less popular, and limiting access population-wide is more difficult in a free economy although this has been achieved for children’s television. Studies have shown children will eat more after watching advertising for foods, and over-weight and obese children are more susceptible to these forms of marketing. As a consequence, manufacturers and retailers are unable to advertise high-fat, high-sugar products at times children may be watching the television, and retailers have been encouraged to remove the same products from checkout areas. Similarly, vending machines have been removed in schools and some hospitals; whilst the patients do not object the staff feel their choices have been impinged. Ultimately, Dr Jebb suggested the challenge is this knowledge into practice.

With 25 years experience in nutrition research, Susan now leads a team of scientists working across a range of public health nutrition issues, with particular emphasis on the translation of nutrition science into policy and practice.

She is Chair of a NICE Programme Development Group developing guidance for the prevention of obesity at a community level and chaired the cross-government Expert Advisory Group on Obesity in England from 2007-11. She is Co-Chair of the Public Health Responsibility Deal Food Network. In 2008 she was awarded an OBE for services to public health.