WHAT’S THE BEST WAY TO LOSE A FEW KILOS?

Humans are very social creatures. We love celebrations and festivities where special foods and drinks are prepared and enjoyed. I call them party foods – those we keep for special occasions. Here in Australia, our summer weather means we tend to have seafood (e.g., prawns/shrimp and oysters) and salads on the menu. Some of us will also have ham and/or roast pork, and barbequed meats and vegetables. Then there’s dessert: a traditional pavlova with mango, berries and passionfruit is my favourite. Champagne, wine, beer, cocktails, dips, crisps/chips, chocolates and other temptations are all around us. And we don’t want to seem impolite.

We can’t be blamed for drinking and eating more than usual and gaining a few kilos. Afterall, it’s perfectly normal to overeat when food is abundant. Primatologist Herman Pontzer showed this in primates that are housed in zoos and research laboratories (1). It even happens in the wild too if extra food is added to the ecosystem. Interestingly, it also happens on a seasonal basis in primates, including humans (2). Gaining a few kilos in summer to make up for any scarcity in the winter. You could say we are primed to gain weight, the trouble being that we’ve taken scarcity out of the equation.

After the festive season, most of us want to lose those extra kilos fast so the waistband is not quite so tight. What’s the most efficient way to do it? The most useless answer is ‘eat less and exercise more’. In my mind that’s a recipe for hunger, a primitive instinct, designed to make you eat enough to avoid the next famine.

In my mind, the safest way to lose a few kilos or more is to use total meal replacements (TMR) in the form of ‘shakes’. When we started the PREVIEW Study (a 3-year diabetes prevention study), I was not a fan of them, nor were my fellow researchers. But then I saw the smile on our participants faces. After 8 weeks, on average they had lost more than 10% of their body weight while consuming 3-4 shakes a day. If they started at 100 kg, they lost 10 kg. They did not feel hungry, they weren’t asked to exercise, simply to drink lots of water. The shakes gave them about half their normal energy (kilojoules/calories) intake but all of their micronutrients, all of their essential amino acids, fatty acids and some fibre as well. We also encouraged them to eat a salad with a low-joule dressing.

There are many brands of TMR on the market, but some taste better than others. In the PREVIEW study, Cambridge Diets donated all the shakes for over 2000 participants (3). The surprising thing about these milkshakes is their ability to make you feel full and satisfied. We don’t normally associate liquids with feeling full, but these have almost half their energy as protein which is known to produce the greatest satiety. The rest of the energy comes from carbohydrate, mostly in the form of sugars. Despite this, they have a low GI and do not lead to blood glucose highs or lows.

The optimal combination of protein and carbohydrate in meal replacements also means you maximise fat loss, rather than muscle loss. Starving yourself is a recipe for losing mostly muscle. In fact, that’s exactly what happened in an experiment where healthy men voluntarily starved themselves for 7 days (4). They spent the time in a metabolic chamber, so the researchers were able to measure breath gases and determine exactly which tissues were being used to support weight loss. The unexpected finding was that muscle loss was three times greater than fat loss – 4.6 kg vs 1.4 kg in 7 days. This makes sense to me because the brain is a greedy organ that preferentially runs on glucose, not fat. When fasting, that glucose comes from gluconeogenic amino acids in muscle.

So, if you’d like to lose a few kilos after the festive season with minimum pain, consider having two TMR shakes a day – one for breakfast and one for lunch, and a normal healthy dinner, for a few weeks. If you wish, have a piece of fruit for morning and afternoon tea, and a simple salad with lunch.

Finally, in case you think I might have something to gain, I have no shares or interests in the companies that make these products. I’m grateful that they make them to high standards and donate generously to research.

Read more:

1. Pontzer. The provisioned primate: patterns of obesity across lemurs, monkeys, apes and humans. Philosophical Transactions of the Royal Society B: Biological Sciences. 2023.
2. Prentice and colleagues. Long-term energy balance in child-bearing Gambian women. American Journal of Clinical Nutrition. 1981.
3. Raben and colleagues. The PREVIEW intervention study: Results from a 3-year randomized 2 x 2 factorial multinational trial investigating the role of protein, glycaemic index and physical activity for prevention of type 2 diabetes. Diabetes, Obesity and Metabolism. 2021.
4. Kolnes and colleagues. Effects of seven days’ fasting on physical performance and metabolic adaptation during exercise in humans. Nature Communications. 2025

Emeritus professor Jennie Brand-Miller held a Personal Chair in Human Nutrition in the Charles Perkins Centre and the School of Life and Environmental Sciences, at the University of Sydney until she retired in December 2022. She is recognised around the world for her work on carbohydrates and the glycemic index (or GI) of foods, with over 300 scientific publications. Her books about the glycemic index have been bestsellers and made the GI a household word.