The Pulse

Why is it so hard to lose weight and keep it off?

by Dr Jocelyn Lowinger

If you've ever tried to lose weight you'll know how easily lost kilograms return. Obesity researcher Dr Priya Sumithran explains what's going on.



[Image source: iStockPhoto | NinaMalyna ]

You work hard for weeks. You say no to your favourite foods. You avoid dinner with friends. You get up early every morning and go for a walk. You notice that your clothes are getting looser.

Yet six months later, the weight has come back. We know weight loss is hard, but keeping it off over the long-term is so much more difficult.

Endocrinologist and researcher from the University of Melbourne Department of Medicine at Austin Health, Dr Priya Sumithran says there are a number of reasons why we regain weight that we've previously lost.

Sumithran, whose research focuses on obesity, says in part it has to do with old habits, but there are also other reasons.

"It is not just behavioural factors, such as falling back into old habits with diet and exercise. There are also biological reasons why we regain weight we've lost," she says.

"When we lose weight there are changes in our hormones that control our appetite, energy and fat storage that encourage us to put on weight. We get hungrier, store fat more efficiently, and burn less energy."

These hormonal changes can affect you for a year or more after you lose weight. This can make it harder to keep weight off than it was to lose weight in the first place, Sumithran says.

The way your hormones control your appetite is complex, with more than 20 different hormones (including, insulin, leptin and gherilin, as well as other chemicals) known to play a role. These hormones work together through a complex system of hormonal pathways to either stimulate or suppress appetite.

Some hormonal pathways work to ensure you get the nutritional intake you need. While other pathways are more related to pleasure you get from eating  the sight, smell and taste of food, as well as social and emotional pleasure food brings. Your food pleasure pathways can override the ones related to nutritional intake, increasing your desire for energy-dense food, even if you don't need it.

But don't be disheartened. Sumithran says it is possible to maintain weight loss.

Those who have sustained weight loss of 15 kilograms or more for at least a year commonly use a number of strategies, including:

monitoring their food intake and consistently eating a low-fat portion controlled diet with little variation.

exercising consistently for at least an hour a day (equivalent to walking 45 km a week) without taking time off for weekends and holidays.

limiting time spent watching TV to around 10 hours a week.

monitoring their weight regularly (eg weekly).

Sticking to these dietary and exercise strategies isn't easy though, especially as you often feel hungrier because of the hormonal changes. And it doesn't help that we live in a society that promotes a sedentary lifestyle and where there's an abundance of (nutrient dense) food.

"That's why preventing weight gain in the first place is so important," Sumithran says.