Liquid meals for weight loss aren’t a new idea, but they’ve come a long way over the past 20 years. Today people often use meal replacement shakes as a practical tool for managing their weight because doing so takes the guesswork out of one meal while still meeting overall energy needs. This blog is about what the evidence says, how they compare to other options, and who tends to get the most out of them.
What Are Liquid Meals?
The term ‘liquid meal’ covers a few different things. A meal replacement shake is specifically formulated to stand in for a full meal. It contains a balance of protein, carbohydrates, fats, and added vitamins and minerals and can be considered as a reasonable nutritional substitute for food.
A protein shake, by contrast, is designed to add protein to your diet, not replace a meal. It typically has little else in the way of nutrients and is usually used alongside your meals.
Then there are food-based smoothies, which provide a somewhat concentrated and easy to consume version of all the foods in the ingredient list. Often, they are based on fruits and vegetables but can also include oats, nuts, seeds and protein powders.
At the other end of the spectrum are liquid-only diets which are called very low energy diets (VLEDs). These are designed to replace all foods and so they are taken in place of breakfast, lunch and dinner. Due to their very low energy content, these are to be used under close supervision from your doctor and are often used for short time frames for a specific medical purpose. For the purposes of this article, I’m talking about using one or two meal replacements shakes per day as part of a broader healthy eating plan.
How Liquid Meals Can Support Weight Loss
The appeal of meal replacement shakes comes down to simplicity. When one meal is already portioned, balanced, and ready in two minutes, it removes a significant source of decision fatigue from your day. Research shows that the more food decisions we make, the more likely we are to default to less nutritious, higher calorie choices.
There’s also solid evidence behind their effectiveness. A 2018 systematic review of 23 randomised controlled trials involving nearly 8,000 people found that incorporating meal replacements led to 1.5 kg more weight loss at one year compared to standard dieting alone and the difference held for up to four years. People using meal replacements with support from a health professional (such as a dietitian) were up to eight times more likely to achieve 10% weight loss compared to those self-directing their diet changes.
Benefits of Using Liquid Meals
• Quick and convenient: ready in minutes, easy to take on the go, and no cooking required.
• Predictable nutrition: every serve delivers the same calories and nutrients, taking the guesswork out of at least one meal.
• Supports structured eating: eating regularly helps moderate your appetite through the day and reduces the urge to graze.
• Reduces decision fatigue: one less meal to plan or prepare means more mental bandwidth for the rest of your day.
Common Concerns About Liquid Meals
Will they keep me full?
This depends on the product. A meal replacement with around 20-25g of protein and at least 5g of fibre should keep hunger at bay for a few hours. Drinking your shake slowly helps too as it takes around 15–20 minutes for the brain to register fullness. Pairing your shake with a large bowl of salad or crunchy vegetables can also help with fullness.
Are they nutritionally complete?
A true meal replacement (as opposed to a protein shake) contains added vitamins and minerals to cover your basic nutritional needs for that meal. That said, shakes can’t fully replicate the phytonutrients found in whole foods. These aren’t classified as essential nutrients, but they do offer real health benefits including reduced inflammation and improved gut health. This is why meal replacements work best alongside a diet rich in vegetables, fruit, and whole grains, not as a replacement for them.
Can I use them every day?
Yes, for most healthy adults, one to two meal replacement shakes per day is considered safe when combined with balanced whole food meals. If you have a medical condition, are pregnant or breastfeeding, or have a history of disordered eating, it’s worth checking with your GP or an Accredited Practising Dietitian first.
Who Liquid Meals Work Best For
In my experience, liquid meals tend to be most useful for:
• Busy professionals who regularly skip breakfast or grab unhealthy lunches on the run
• People who find meal planning overwhelming and want a simple, structured starting point
• Anyone managing portions for the first time, who benefits from the clarity of a fixed-calorie meal
• Those who tend to graze or over-eat at certain times of day, and want a satisfying alternative
• People who want a convenient backup plan for days when healthy eating would otherwise fall apart
They tend to be less useful as a long-term, standalone strategy. Meal replacements are most effective as part of a broader plan that includes whole food meals, regular movement, and some support from a health professional.
How to Use Liquid Meals Effectively
A few practical tips to get the most out of meal replacement shakes:
• Replace one meal per day to start, usually the one that’s most rushed or the one you find the hardest to make nutritionally balanced.
• Add a piece of fruit or some veggie sticks alongside your shake to boost the nutritional quality of that meal and increase satisfaction.
• Check your protein and fibre. Aim for a shake with around 20-25g of protein and at least 5g of fibre per serve (such as a Tony Ferguson Classic Shake) to maximise fullness.
• Keep your other meals balanced. A meal replacement works best as a complement to whole food meals, not a shortcut to avoid them. Fill half your dinner plate with vegetables, include a palm-sized portion of lean protein, and choose high-fibre carbohydrates.
• Stay consistent, not perfect. Missing a day or switching it out for a real meal isn’t a problem. Consistency over the week is what drives results.
• Pair with regular movement. Liquid meals support calorie reduction, but combining them with daily activity makes a meaningful difference to both weight loss and long-term weight maintenance.
The key takeaway
Liquid meals can be a useful tool for weight loss when they’re used strategically. They simplify one meal, reduce decision fatigue, and provide reliable nutrition on busy days. The evidence supports their effectiveness for weight loss, particularly when combined with professional support.
That said, they’re not a magic solution and they’re not meant to replace real food indefinitely. The goal is to use them as a practical scaffold while you build the eating habits and routines that will serve you well long after the shake has done its job.
