burger and chips on plate

How to prevent weight regain

23 March 2020
Ensuring long-term weight-loss success
Ever lost weight, only to put it back on…and then some? It’s not a lack of willpower, it’s biology - your body’s physiological responses lead you to put it back on.

Dr Nick Fuller from the Charles Perkins Centre at the University of Sydney and author of the Interval Weight Loss program sheds light on how your biology is preventing you from succeeding and what you can do to ensure long-term weight-loss success.

1. Metabolism

Your metabolic rate is how much energy you burn at rest. It is determined by how much muscle and fat you carry. As muscle is more metabolically active than fat (i.e. it burns more energy than fat), a person with a higher muscle mass will have a faster metabolic rate than someone of the same body weight with a higher fat mass.

With weight loss, your metabolism will decrease because your body mass decreases. However, there is a decrease in your metabolism by a further 15 per cent beyond what can be accounted for by a reduction in body mass. This means for every diet you attempt the rate at which you burn off your food slows by 15 per cent. Worse still, research has shown that even after stacking the weight back on, your metabolism doesn’t recover. 

Tip: Exercise plays a critical role in preserving your muscle mass when you lose weight. Find activities you enjoy and can stick to them long-term. 

2. Energy source

At rest, your body is predominantly burning fat stores. When you lose weight, your body will start to work differently and shift the type of energy source you use, from fat to carbohydrates to ensure your body holds onto its fat. This ensures you burn less energy at rest and consequently you start to regain the weight you lost. 

Tip: Keep yourself accountable by jumping on the scales once per week and monitor the trend in your weight over time. 

3. Appetite hormones

Your appetite hormones play a large part in ensuring your day-to-day weight stays stable. For example, when you are hungry, the stomach releases a hormone called ghrelin to tell the brain to tell you to eat. When it’s time to stop eating, other hormones are released from both the gut and fat tissue to signal that. But when you lose weight these appetite hormones will work differently, suppressing your feeling of fullness and telling you to eat more.

Put simply, your body begs you to binge when you deprive it of food. Even after you have regained the weight you lost, your appetite hormones do not return to the same levels they were before dieting and you continue to feel hungry after stacking the kilos back on.

Tip: Don’t deprive yourself of food when you set out to lose weight; eat more, not less, and give your body the nutrition it needs.

4. Autonomic nervous system 

The autonomic nervous system regulates body functions like heart rate and breathing rate. It is made up of the sympathetic and parasympathetic nervous system. The sympathetic nervous system is referred to as the ‘fight or flight’ system, while the parasympathetic nervous system is referred to as the ‘rest and digest’ system. The systems work to oppose one another, whereby one will activate a physiological response and the other will inhibit. Not only will your metabolism slow when you lose weight, but it also means your heart rate and breathing rate will decrease as the parasympathetic nervous system takes control

Tip: To prevent your metabolism slowing, impose “intervals” every second month, to allow your body the rest it needs.

5. Thyroid gland

The thyroid gland is the gatekeeper to your metabolism. A healthy thyroid means your metabolism is firing, and a sluggish or poorly functioning thyroid means the amount of energy you should be expending will be compromised. Under normal circumstances, your thyroid gland will produce hormones, but when you restrict the amount of food you eat, fewer of these hormones are secreted which ends in a reduction in the amount of energy you burn at rest. 

Tip: Forget calorie counting. Instead, load up your plate with a wide variety of colours and slow down your consumption by using chopsticks or a teaspoon.

6. Adrenal gland

The adrenal glands produce a range of hormones, including the stress hormone cortisol. When a stress like dieting is imposed on the body, the pituitary gland stimulates the release of a hormone, which then produces cortisol. An excess of cortisol production leads to weight gain and when you restrict the amount of food you eat,  the cortisol level in your blood increases

Tip: Set a goal that is a lifetime event, rather than a moment in time. The all-or-nothing approach and the 4, 8 or 12-week weight loss programs don’t work long-term.

7. Brain function

Typically, diets tell us to restrict certain foods in order to reduce calorie intake. However, restricting or cutting out certain foods or food groups on a diet results in a change in brain function - the reason you start craving the morning toast the exact moment you decide to eliminate bread is because of  heightened activity in the reward-system part of the brain. You give into your cravings because those foods give you pleasure and they release the feel-good chemicals called endorphins and the learning chemical called dopamine, which remembers that feel-good response next time you see it. But that’s not the full extent of it.

The other significant change that a person will experience with dieting is a reduced activity in that very clever part of the brain called the hypothalamus and areas involved in the emotional control of food intake. This results in a decreased control of food intake and an impairment in the ability to sense a positive energy balance following dieting. This ends up triggering a psychological response dubbed the ‘what-the-hell effect’ – a vicious cycle of indulgence, followed by guilt, followed by greater indulgence. You end up eating the whole packet of Tim Tams instead of just the one. 

Tip: Don’t deprive yourself completely of your favourite foods. Wean yourself off them slowly and aim to include them just once per week.


More information:
5 reasons why diets don't work and what to do instead


Research Leader

Dr Nick Fuller

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