APPENDIX 29
Memorandum by Medical Research Council
(OB 50)
INQUIRY ON
OBESITY
The Medical Research Council (MRC) welcomes
the opportunity to provide a submission to the Health Committee
in its inquiry on Obesity.
INTRODUCTION
1. The MRC is the principal public sector
funder in basic and applied research relevant to medicine. The
Council's mission is to:
— encourage and support high quality
research with the aim of maintaining and improving human health;
— train skilled people, and advance
and disseminate knowledge and technology to help meet national
needs for health, quality of life and economic competiveness;
and
— promote public engagement with medical
research.
2. Thus the Council's contribution to tackling
obesity involves funding relevant basic and clinical research,
contributing towards the necessary supply of skilled people and
raising public awareness of and support for new scientific developments.
3. The Council invests in research and training
through research grants, mainly to scientists based in higher
education institutions, support for research in its own Units
and Institutes, and personal awards for research training and
career development.
4. Last year, the MRC spent £17.1 million
on research on nutrition, much of which is pertinent to obesity,
ranging from basic mechanisms to clinical research. The MRC directly
funds institutes undertaking research in areas of relevance to
this Inquiry:
— MRC Dunn Human Nutrition Unit (Director
Sir John Walker), which focuses on the molecular mechanisms of
energy generation in mitochondria, the molecular basis of inherited
mitochondrial diseases, and the role of nutritional factors in
relation to DNA damage and risk of cancer and other chronic diseases
in humans;
— MRC Resource Centre for Human Nutrition
Research (Director Dr Ann Prentice), which undertakes research
on the influence of diet and lifestyle on chronic diseases, including
obesity and its metabolic co-morbidities, using highly controlled
experimental studies and community interventions;
— MRC Social and Public Health Sciences
Unit (Director Professor Sally Macintyre), which is interested
in social and environmental influences on diet and physical activity,
and how these might contribute to obesity.
5. The MRC has research links and interactions
with other organisations, focussing on diet, nutrition and obesity.
An eight-year research initiative in nutrition, which ended recently,
was run jointly between the MRC and the Department of Health.
Programmes within this included identifying opportunities for
and barriers to dietary change, and developing and evaluating
interventions aimed at achieving prevention of obesity. The Food
Standards Agency (FSA) has a nutrition research theme, which includes
programmes on food acceptability and choice, food choice inequalities,
colonic health, dietary lipids and dietary surveys. Some of the
research of these programmes has been undertaken by the MRC Centre
for Human Nutrition Research and the MRC Dunn Human Nutrition
Unit. The BBSRC has a diet and health research theme, which aims
to increase understanding of the relationship between diet and
health in the context of both public health and consumer interests.
The research undertaken in this theme is complementary to the
research aims of the MRC.
6. The MRC and the BBSRC undertook a review
of human nutrition research, in 2001, which aimed to: inform future
research and strategic planning; highlight interfaces with the
FSA; and form the basis of a Foresight Associate Programme in
human nutrition research that could feed into the work of the
Foresight Panels in developing visions and recommendations for
the next 5-15 years. Amongst its conclusions, the review considered
that there was a need for further research studying the contribution
of food, diet and nutrition to the major non-communicable diseases,
and to understand what people eat and the cultural, social, physiological
and economic factors which define food choice and nutrient balance.
THE HEALTH
IMPLICATIONS OF
OBESITY
7. Obesity has a significant impact on human
health, contributing to the onset of disease and to premature
mortality. Diseases associated with obesity are listed in Table
1, and evidence has shown that increased body weight is associated
with increased death rates in certain diseases, such as cancer.
Most of this data is derived from research in the USA. Whilst
there is little reason to believe the associations are different
in the UK, evidence will emerge from important national surveys
including Birth Cohorts, Avon Longitudinal Study of Pregnancy
& Childhood and BioBank in which the MRC has made significant
investment. Obesity represents a substantial burden to the healthcare
system and the wider economy. The models used to assess these
costs are imperfect, but even a conservative estimate by the National
Audit Office (2001) suggests the cost of obesity to the NHS is
£0.5 billion with a further £2 billion to the UK economy
in lost productivity.
TABLE 1: RELATIVE RISK OF HEALTH PROB LEMS
ASSOCIATED WITH OB ESITY
TRENDS IN
OBESITY
8. The prevalence of obesity in the UK has
trebled in the last 20 years from 6 and 8% of men and women in
1980 to 21 and 23.5% respectively in 2001. This increase shows
no sign of slowing down and is closely tracking the trend seen
in the USA. Further, the prevalence of obesity in children and
adolescents is also increasing. For example in children aged 10-11
years the prevalence of obesity has increased from 2.7% in 1983
in the British Survey of schoolchildren to 9.3% in the latest
National Diet and Nutrition Survey (NDNS) of Young People.
9. There is a clear link between social
inequalities, ethnicity and obesity, especially in women. For
example, the Heath Survey for England shows that obesity is almost
twice as common in women in social class V relative to social
class I and the prevalence of obesity is higher in ethnic minority
groups than Caucasians [Health Survey for England: The Health
of Minority Ethnic Groups 1999]. There are also important differences
in the distribution of body fat which may exacerbate some health
risks, in particular diabetes and coronary heart disease in some
groups, especially Asians. Differences in the prevalence of obesity
are likely to underpin many long-term health inequalities and
understanding these variations within the UK population is important
to inform the development of appropriate intervention strategies.
10. Recent research by Dr Jebb at the MRC
Resource Centre for Human Nutrition Research has shown that similar
disparities exist in children. Analysis of the NDNS of young people
aged 4-18y, showed that Asians were almost four times as likely
to be obese as white children and adolescents. Amongst white youngsters,
those in the lower social classes (social classes IV and V) were
three times more likely to be obese than other children.
11. In many developing countries obesity
co-exists with undernutrition. Although obesity is relatively
uncommon in African and Asian countries, it is more prevalent
in urban rather than rural populations. Data on the incidence
of obesity is limited, though evidence suggests that it is increasing.
A study in Mauritius showed an increase in the prevalence of obesity
in men and women between 1987 and 1992 from 3.4 to 5.3%, and from
10.4 to 15.2%, respectively (World Health Organisation, 1998).
WHAT ARE
THE CAUSES
OF THE
RISE IN
OBESITY IN
RECENT DECADES?
12. Identifying the causes of obesity is
hampered by a lack of fundamental understanding of the normal
control of human body weight. The MRC is currently funding two
Career Establishment Grants investigating the function of hypothalamic
circuits in controlling body weight, and the role of the vagal
complex in integrating hunger and satiety signals.
13. The increase in obesity in the population
is likely to be due to a range of contributory factors. Although
the rise in obesity cannot be explained solely by changes in the
genetic background of the population, research has shown that
genetic factors play an important role in an individual's susceptibility
to obesity. Research by Professor O'Rahilly (MRC Programme Grant
holder) has described human genetic defects leading to severe
early onset obesity (Nature 1997, Nature Genetics 1997). Recent
studies are showing more common genetic variants which may have
a broader role in determining body fat mass across the population.
14. There have been large changes in diet
and lifestyle over the last two decades which have contributed
greatly to the increase in obesity. Previous research undertaken
by Professor Prentice (MRC Programme Grant holder) and Dr Jebb
(MRC Resource Centre for Human Nutrition Research) has been instrumental
in identifying the importance of sedentary lifestyles as a risk
factor for weight gain (Prentice & Jebb, 1995). Their experimental
studies also demonstrated the phenomenon of "high-fat hyperphagia"
whereby individuals are more likely to over consume high-fat foods
of high energy density (Prentice, 1998).
15. The importance of inactivity as a cause
of obesity is well-accepted, despite relatively poor measurements
of secular trends in activity. The role of diet has proved more
controversial. However it is clear that obesity only occurs due
to a mismatch in energy intake and expenditure, rather than in
one or other component alone and hence inappropriate diet is an
important element in the causation of obesity.
WHAT CN
BE DONE
ABOUT IT?
16. In tackling obesity a range of different
approaches, including medical, physical and social methods, may
be required. However, there is a need for research to understand
both the contribution and importance of specific factors linked
to obesity, and also the effectiveness and practicality of future
interventions for both the prevention and treatment of obesity.
17. Specifically, further research is required
in the following areas:
— the basic biological mechanisms that
cause obesity;
— the role of genetic factors in the
susceptibility to and development of obesity;
— the impact of life-style and behaviour,
including physical activity, sedentary inactivity and food choice,
on the risk of weight gain;
— the behavioural patterns that influence
the choices and decisions an individual makes, and how such behaviour
can be changed;
— the link between social class and
obesity, and ethnicity and obesity;
— life-time risk factors and health
consequences: in particular the long-term health consequences
of developing obesity during childhood and adolescence and whether
the factors contributing to obesity in children differs to those
in adults;
— life-course studies, as there is
evidence that what happens during development in the womb and
childhood has an impact on how the body responds to changes in
physical activity, diet and lifestyle later in life;
— the health effects of repeated weight
gain and weight loss, including the psychosocial impact;
— collection of high-quality data on
obesity in developing countries.
18. Research in the above areas will inform
strategies for the primary and secondary prevention of obesity.
Promising data in the treatment of obesity has emerged from a
small number of large, long-term clinical trials. However, there
is a need for more studies to assess the impact of interventions
including diet, activity and behavioural modification, as well
as medical and surgical treatments, and for trials investigating
the use of multiple interventions to tackle obesity. Further,
research should be effectively translated for applied use.
19. To date many interventions have focused
on individuals, using classical medical models of disease management.
There is growing awareness that interventions to prevent obesity
may require a broader approach, for example behavioural, social
and medical, which will require greater involvement from all sectors
of society, beyond the medical and scientific community. This
may require new organisational structures to be developed, and
consideration needs to be given to the role that particular organisations
can play in communicating strategies to treat and prevent obesity
to the public.
20. MRC is funding research that will add
to the current understanding of the causes and health impacts
of obesity, and advance prevention and treatment strategies. Examples
of current and recent research, ranging from basic biological
and genetic studies through to health interventions, include:
— mechanism of action of the appetite
suppressing hormone leptin (Dr David Carling, MRC Clinical Sciences
Centre)
— understanding the genetic basis of
human obesity (Professor Steve O'Rahilly, Programme Grant; Professor
Philippe Froguel, Programme Grant)
— impact of nutrition during childhood
and adolescence on risk factors for adult disease (Professor Alan
Lucas, Programme Grant)
— determining child and adulthood risk
factors for obesity, and how early and later life factors might
act in combination (Dr Parsons, Clinical Research Training Fellowship)
— research to consider dietary patterns
and the behavioural determinants of food choice (MRC Resource
Centre for Human Nutrition Research)
— studies on environmental barriers
to and facilitators of healthy eating and activity patterns, and
on the socio-cultural attitudes to eating and body weight (MRC
Social and Public Health Sciences Unit)
— prospective cohort study into the
interaction between genetic factors and energy expenditure in
determining weight gain (Professor Nick Wareham, Component Grant)
— clinical trial of the efficacy of
a family based programme to increase physical activity among individuals
at high risk of diabetes (Professor Ann-Louise Kinmonth, Clinical
Trial)
— development of better methods for
measuring and defining obesity, especially in children (Professor
Tim Cole, MRC External Scientific Staff and Programme Grant holder).
In addition, Council is currently considering
the development of an Epidemiology Unit in Cambridge focusing
on the following research areas: (i) determinants of adult obesity
and related metabolic disorders; (ii) determinants of fetal growth
and childhood obesity; (iii) measurement and epidemiology of physical
activity; and (iv) translating epidemiological observation into
preventative action.
ARE THE
INSTITUTIONAL STRUCTURES
IN PLACE?
21. MRC understands that there is a lack
of trained health professionals in the obesity field. Investment
will therefore be needed to equip practitioners to translate effective
intervention strategies from research into everyday clinical practice.
Training health professionals would be the responsibility of other
agencies.
RECOMMENDATION FOR
NATIONAL AND
LOCAL STRATEGIES
22. Research needs to feed into Government
to enable a clear overarching obesity strategy to be developed,
since it is apparent that effective prevention and treatment of
obesity will require the use of multiple, coordinated interventions
at different levels. The MRC has close links with agencies such
as the Department of Health and the FSA, and meetings are held
to discuss research developments, policies and areas for joint
working.
CONCLUSIONS
23. The Council supports a range of research
on obesity, from the molecular mechanisms of obesity through to
interventions looking at behavioural change. In its Vision for
the Future, which is an exercise in thinking ahead about how scientific
opportunities and health needs might develop over the next decade,
MRC has highlighted obesity and diabetes. We believe that MRC's
research will enable the Council to make a significant contribution
to the development of any future strategies to combat the rise
in obesity.
April 2003
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