Hunger aims: focus on hormone-obesity link

Prof Dave Grattan uses a cross-trainer at the Moana Pool gym. Photo by Linda Robertson.
Prof Dave Grattan uses a cross-trainer at the Moana Pool gym. Photo by Linda Robertson.
Otago is a province with a rich history of establishing firsts. We have led the way in many fields and that tradition continues. Researchers at the University of Otago are attracting international attention, with some granted millions of dollars for cutting-edge projects. So what are they up to? Reporter John Gibb, in a fortnightly series, does his own research on the researchers.

Blaming people for being overweight has failed, and health campaigns to counter New Zealand's growing obesity epidemic should recognise the key role played by hunger-linked hormones in weight control.

That is the view of internationally respected University of Otago researcher Prof Dave Grattan.

One study has ranked New Zealand as the world's third-most-overweight developed country, behind the United States and Mexico.

Prof Grattan is a neuroendocrinologist and an inaugural member of the Otago Centre for Neuroendocrinology, which is the biggest research cluster of its kind in the southern hemisphere.

Neuroendocrinology investigates how the brain controls hormones, and how hormones affect the brain.

Hormones are chemical substances that regulate many important body functions.

Prof Grattan said New Zealand's public health strategy had largely ignored ''the biological and genetic causes of obesity''.

And by tending to blame people for being overweight, this approach had ''compromised our ability to face this condition rationally''.

And the obese then felt guilty for ''failing to meet society's expectations''.

Many people who were not overweight assumed that because they could maintain a healthy bodyweight, through what they termed their ''choices'' and''lifestyle'', that other people should also be able to do so.

But people who were not overweight often did not consider they might simply have the benefit of ''lean'' genes.

There was also a reluctance to support spending public money to counter obesity, because it was thought that obese people simply lacked willpower and ''should just eat less and exercise more''.

But this ignored the key point that lean people probably found it ''relatively easy to eat a smaller portion'' because they were not hungry.

''On the other hand, an obese person is hungry and therefore eats more.''

Attempts to prevent obesity using education, a healthy diet and exercise programmes had failed and ''we can no longer ignore the biology'', Prof Grattan said.

There were fears in some quarters that greater emphasis on discussing the brain's control of appetite could result in some people becoming ''fatalistic'' about their eating habits.

But Prof Grattan believed that moving away from blaming people for what was at least partly a genetically influenced eating response would be positive.

And people would then understand more realistically the weight-control challenges they faced.

Research in this field could well, in future, also help provide much clearer early identification of individual people who are at greater risk of excessive weight gain.

In June, Prof Grattan, fellow anatomy department researcher Dr Christine Jasoni and Associate Prof Colin Brown, of the department of physiology, received a Health Research Council grant of nearly $5 million for their study entitled ''Healthy Pregnancy, Healthy Babies'', which looks at the role of hormones, including prolactin, in pregnancy.

Prolactin is elevated during pregnancy, and may play a direct role in stimulating appetite -through an action in the brain- as well as indirectly, by suppressing responses to other factors that normally reduce appetite.

The incidence of obesity was growing throughout society and most obese individuals appeared to become less responsive - ''resistant''- to the usual appetite-limiting effects of hormones such as leptin or insulin, he said.

''Our work has shown that pregnancy also increases appetite and encourages fat deposition by making the brain resistant to these hormones.''

In evolutionary terms, such weight gain was an ''adaptive'' response, enabling mothers to store energy to meet the future demands of foetal growth and lactation.

But excess weight gain during pregnancy resulted in increased risk of pregnancy complications, including diabetes, hypertension and premature birth.

And adverse long-term effects included shifting the mother's weight to ''a new, higher set point'' from which it was hard to lose weight.

And ''something of a vicious cycle'' had developed- given that growing evidence suggested that obesity during pregnancy might predispose the offspring to obesity, he warned.

Born in Upper Hutt, Prof Grattan grew up in nearby Wellington, where his major interests were sport, ''especially rugby'', in which he represented that city at various age group levels.

After attending Victoria University of Wellington, he ''rapidly got captured by the world of biomedical research''.

He was ''still a big sports fan'', but now watched, rather than played, and visited the gym several times a week.

 


SNAPSHOT

 Name and age: Dave Grattan, age 50.

Occupation: Professor, anatomy department, University of Otago.

Qualifications: Include PhD in physiology, Victoria University of Wellington, 1991.

Short work history: Includes Otago lecturer in anatomy, 1995; inaugural member, Otago Centre for Neuroendocrinology, established 2003.

Proudest achievement: His selection as editor-in-chief of the British-based Journal of Neuroendocrinology, and the journal's only non UK-based editor in its 25-year history, reflected international recognition of his work.

 


THE CHALLENGE
UNDERSTANDING BIOLOGICAL MECHANISMS REGULATING BODY WEIGHT, INCLUDING IN OBESITY.

What is your research about?

My research is in neuroendocrinology: how the brain controls our hormones, and, conversely, how our hormones affect our brain. I am particularly interested in how hormones from the body interact with the brain to control appetite and glucose homeostasis, and how dysregulation of this system plays a major role in obesity and type 2 diabetes. Homeostasis is the body's tendency to maintain equilibrium within its internal environment, even when facing external changes.

Why is it important?

One of the biggest risks facing us is the obesity epidemic - and the downstream consequences, particularly type-2 diabetes. Globally, more than two billion people are overweight or obese, and this is responsible for significant morbidity and mortality.

Most interesting aspect of your research?

When you study the interactions between metabolic hormones and the nervous system, the precision by which these unconscious homeostatic systems work to balance energy intake with energy expenditure over a long period is amazing.

How is it unique?

Our approach to use appetite regulation during pregnancy as a model to understand the biological influences on food intake is internationally unique, providing novel insights into aspects of the appetite regulation system.


 

 

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