Meal Replacement Shakes: An easy source of nutrition or a liquid scam?

The history of portable liquid nourishment is nothing new.

A mainstay of the Roman army diet was puls, a porridge made of hulled wheat and boiled water to which salt and animal fat or olive oil would be added. Genghis Khan’s Mongol warriors subsisted on dried milk curd and fermented mare’s milk. And 18th and 19th century sailors and explorers often relied on “portable soup” – cubes of gelatinous reduced animal fat which would be reconstituted – as an easily transportable, albeit somewhat unpalatable, source of nutrition.

It wasn’t until the 20th century, however, that the idea of replacing most, or all, of one’s daily meals with a reconstituted liquid substitute really took off.

Initially popularised by American chemist John Dorrance’s invention of condensed soup in 1897 (he later went on to become president of the Campbell’s soup company), the idea received impetus during the First World War. After all, if “an army marches on its stomach” (an oft utilised quote attributed to Napoleon Bonaparte), then an army that required a soldier to only carry three small packets a day to keep his stomach full, would surely march even more efficiently.

In the 1920s newspaper cartoons poked fun of the idea of large meals being dispensed as a single small pill, and the 1960s animated sitcom “The Jetsons” would often show the family utilising their “dial-a-meal” machine to produce meals in pill form.

While the meal-in-a-pill is yet to be invented, there is certainly no shortage of meal replacement products on the market, whether they be in the form of shakes, soups or bars. In 2018, the global meal replacement products market was estimated to be worth more than $21 billion AUD annually, with a projected annual growth of 6.5 per cent.  

Meal replacement shakes are prepared formulas that come in either ready-to-drink or powdered form. They aim to provide your body with the equivalent of a full meal’s worth of nutrients in each serve, with a minimum number of kilojoules.

“They were originally intended for people who needed to lose weight rapidly and they can still be used for this purpose,” said dietitian Karissa Deutrom, who is based in Adelaide. “Unfortunately they only work while you consume them, and this can be difficult to maintain over the long term.”

Weight loss tool

Dozens of studies conducted in the past decade confirm that the use of meal replacement shakes can lead to rapid and significant weight loss, with the convenience of the pre-packaged product helping with a higher overall dietary compliance than is traditionally seen with conventional weight-loss programs.  

A report published in the journal Public Health Research and Practice in March this year highlighted the appeal of the meal replacements’ simplicity. An online survey published last year in the journal Behavioural Sciences found that over 70 per cent of health care professionals working in weight management across Australia had prescribed meal replacement products to their patients at some point in their practice. And a 2019 systematic review published in the journal Obesity Reviews collated the results of 23 studies involving over 7880 participants. The researchers found that when meal replacement products were utilised as part of a diet there was greater weight loss at one year compared with diets that did not incorporate them.    

“Formulated meal replacement shakes are an effective evidence-based method for achieving weight loss,” Deutrom said. “They work best for people who regularly skip meals, and are handy to use at work. They can be expensive though, and limit your enjoyment of eating with others.”

University of Newcastle food scientist and nutritionist Dr Vincent Candrawinata cautions that if you are not careful, meal replacement shakes can actually increase one’s daily kilojoule intake.

University of Newcastle scientist and phenolic antioxidants expert Dr Vincent Candrawinata

“Many people think that, ‘Oh, let me drink this slim shake’, and then, half an hour later, because our digestive system is not built to experience satiety from a liquid diet, you eat a piece of toast. So not only do you have the 200 calories from the shake, you also have the 150 calories from the toast. One of the first things I tell clients who need to lose weight is, ‘Don’t drink all your calories’.”

Candrawinata has had clients who have successfully lost weight with meal replacement shakes but only when they were very disciplined about it and reduced their overall kilojoule intake. “If you really want to lose weight that way, it can be possible, however losing weight is also about sustainability.”

Maintaining one’s weight loss is a topic obesity expert Dr Nick Fuller has spent more than a decade researching. As part of his work at the University of Sydney’s Charles Perkins Centre he has trialled dozens of the most popular diets and weight loss products on the market and says that weight loss via meal replacement shakes is usually not sustainable over the long term.

“You could use them to kickstart your journey but you’ve still got to learn how food can be part of your day-to-day plan,” said Fuller, who founded the Interval Weight Loss program which he says is the only program scientifically proven to prevent weight regain. “If you don’t form healthy habits, you’ll eventually go back to your old ways. So you’ve got to think about long-term healthy habits that you can sustain.”  

How healthy are meal replacements?

“You really have to do your research if you want to use a meal replacement regularly,” says Surfers Health Medical Centre Practice Principal Dr Mark Jeffery, a general practitioner with more than 30 years’ experience. “I’ve certainly had patients who have been using certain branded meal replacements that are actually very high in sugar, or lacking in vital ingredients.”  

Even though meal replacement products contain protein, Jeffery does not believes they provide us with all the essential amino acids needed to build muscle and produce energy. “They can be useful if you’re on the run and you use it to replace a meal purely as a convenience, but you should still certainly not use them to replace all your meals. If you really want to look at your diet, and look at ways you can improve your gut health and boost your immune system, then you need to be eating a variety of food that is nutritious.”

Deutrom says a meal replacement shake may still be a better choice than no meal at all though. “Busy people often skip meals, and this can lead to a lack of energy, nutrient deficiencies and weight gain. Formulated meal replacement shakes are quick to prepare and consume, and better for you than skipping a meal,” she said. “But for busy people who don’t need to lose weight, a smoothie made with milk, yoghurt, fruit, nuts and seeds would be a more nutritious option to drink.”

Photo credit: Anthony Shkraba

The pitfall of using a very low calorie meal replacement is that the consumer is likely to experience an energy slump and then succumb to a quick sugar fix, said Deutrom. “We draw a lot of satisfaction from chewing and swallowing “real food”, and we are more likely to meet our nutritional needs from enjoying a wide variety of foods every day.”  

If you are going to supplement your diet with a meal replacement, Deutrom advises reading the label carefully. “Choose a ‘Formulated Meal Replacement’ as they adhere to the guidelines governed by Food Standards Australia and New Zealand (FSANZ),” she said. “As a minimum they must contain at least 12 grams of protein per sachet, and a quarter of the recommended daily intake of key nutrients. And choose a product with added fibre, such as psyllium, guar or inulin, so you feel fuller for longer.”  

It’s also worth taking note of the product’s sweetener. “You may want to choose one that is sweetened with something natural like stevia or erythritol, rather than something artificial like aspartame because I do not believe that using a chemical sweetener is worth the calories saved,” Candrawinata said. “Not only is it artificial, but some studies have shown that it actually makes you feel hungrier later on.”  

Relying too heavily on meal replacement produces may also raise your cholesterol levels, warns Candrawinata. “The shake may alter the way your body produces cholesterol because of the blood sugar profile, and then your endogenous cholesterol level goes up.”

To replace or not to replace?

Most experts agree that choosing to utilise meal replacement products for either your weight loss journey or simply for your own convenience is an individual choice.

“The more people I meet and the more stories I listen to, the more I am becoming mindful that it is almost arrogant to tell people what they should eat and what they should do in their life,” said Candrawinata. “So every time I share my opinion, I’m also mindful that what works for me, or even what works for most people, might not work for you.”

Psychotherapist and author of the podcast ‘Misunderstandings of the Mind” Jason Shiers says it’s useful to look at your motivation when considering whether or not to incorporate a nutritional supplement like a meal replacement into your diet.

“I couldn’t advise anyone whether meal replacement shakes are good or bad, but I can advise everyone that you will know when they’re good or bad for you,” he said. “If you’re trying to fix the outside of your body, like its shape or size, by taking a meal replacement, then I’d say that’s a good indicator that it’s probably not a good thing for you,” he said. “But every person has access to their own wisdom and if you have a sense that they would be good for your nutritional balance, then by all means listen to your own wisdom.”

Watch the extended interview with psychotherapist Jason Shiers here

Deutrom hopes that people will prioritise their health and make the best choices to suit their lifestyle.

“To maximise your health, it’s important to find a formula you can stick to for life,” she said. “If that involves replacing one meal a day with a meal replacement, then that’s great. But to ensure your nutrient needs are met in a sustainable way, you might like to try the Mediterranean diet with calorie limits. Featuring mostly vegetables, legumes, nuts, wholegrains, fruit, oily fish and olive oil, this eating pattern can be as effective for weight loss, with the bonus of improved metabolic and mental health plus longevity. Plus you will get to enjoy eating delicious ‘real’ meals with the people you love.”

  • Watch as Dr Nick Fuller explains how the Interval Weight Loss program works and how it can help you lose weight and keep it off for the long term:   

Suvi Mahonen is a Surfers Paradise-based journalist. Her work appears in The Australian, the Australian QuarterlyMamamia and other health and lifestyle publications. Follow her on FacebookYouTube and online art-selling platform Redbubble.

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