Weight loss smoothies are big business these days. You might have seen ads for them making tantalising claims… Quick, easy, satisfying, nutritious – a complete meal in a drink! This can make them a tempting option for people trying to lose weight. But does the scientific evidence back them up?
In this article – our in-house nutritionist explores the pros, cons, and scientific evidence supporting both sides of the smoothie diet argument so that you can make an informed decision for yourself.
Our aim is to provide a balanced view that explains all the aspects to consider so that you have a complete picture.
Different Types of Smoothie
Let’s start by clarifying the different types of smoothies that often get categorised into this group. Not all of them are created equal and their ingredients will influence whether they are helpful for weight loss or not.
- Homemade smoothies – usually contain fresh or frozen fruit, leafy greens, milk or juice, sometimes protein powder, or other flavourings like herbs and spices.
- Packaged smoothies – are sold ready-made in bottles and cartons, these also contain fruit and veg along with flavourings and preservatives.
- Meal replacement smoothies – commonly marketed as weight loss shakes, these are either designed to provide essential nutrients in liquid form or claim to stimulate fat burning.
Each smoothie needs to be judged on its own merit. It wouldn’t be accurate to say that all homemade smoothies are healthy and all others aren’t, because it depends on the ingredients that they contain.
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Benefits of Smoothies for Weight Loss
The weight-loss benefits associated with smoothies include increased nutrient intake and fast results, along with speed and ease of preparation.
- Increases intake of fruit, veg, and associated nutrients like carbohydrates, fibre, vitamins, and minerals.
- Calorie restrictive diets like those involving meal replacement shakes can lead to quick weight loss (i.e. within a few weeks) in the short term.
- Smoothies are often quicker to prepare than meals.
- Making a smoothie is sometimes easier than a meal too since there’s no need to research healthy recipes, carefully measure ingredients, track calories, or basically think in any way!
- When used as substitutes for unhealthy snacks or meals, it can displace calories from these poor nutritional sources.
Now let’s examine the other side of the coin…
Disadvantages of Using Shakes to Lose Weight
The disadvantages of following a smoothie diet include lack of varied nutrients, not providing long-term results, not feeling full afterward, high cost, scientifically unproven benefits, and inadvertent weight gain.
- Smoothies don’t always provide a varied nutrient intake or form a balanced diet as they’re sometimes missing protein and healthy fats.
- Not a long-term solution as they don’t lead to a lifestyle change – as soon as you stop drinking them, the weight will immediately return (which can lead to yo-yo dieting and related issues).
- Liquids aren’t as satisfying or filling as solid food which can leave you feeling hungry and make these types of diet harder to stick with.
- Prepackaged diet smoothies and meal replacement powders are expensive to buy.
- Many of the bold marketing claims made by so-called ‘fat-burning smoothies’ aren’t proven by science.
- Some kinds of sugar-laden smoothies (e.g. McDonald’s or Innocent smoothies) can lead to inadvertent weight gain.
- They may not always contain the ingredients or nutrients that they claim in the quantities stated on the packaging.
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What Does Scientific Evidence Say?
The scientific research on meal replacement shakes isn’t particularly positive. Studies that weight loss companies promote on their websites aren’t usually very rigorous. They typically involve small numbers of participants and only measure short-term outcomes, which makes their results less valid.
One systematic review examined 45 studies of commercial weight-loss programs, including Optifast and Slim-Fast shakes. The Optimfast results showed successful short-term weight loss but these tailed off after 6 months. For Slim-Fast, it concluded that results were mixed so no concrete outcome either way.
Commercial weight-loss programs don’t seem to be very effective in general. Another systematic review looked at 25 weight loss studies involving meal replacements, calorie-counting, and pre-packaged meal programs…
They found that 57% of the participants lost less than 5% of their initial body weight and over 30% dropped out. The researchers concluded that commercial weight-loss programs frequently fail to produce weight loss and many consumers find them unsustainable.
So, Are Smoothies Good for Weight Loss?
Smoothies can be good for weight loss as part of a balanced diet and active lifestyle. They aren’t a quick fix or standalone solution so you need to combine them with other weight loss efforts.
- Drink plenty of water
- Eat a variety of different fruit and veg (smoothies can help with this element)
- Consume lean protein and healthy fats
- Take regular exercise
- Get good quality sleep
The best smoothies for weight loss are those that replace an unhealthy eating habit such as snacking on crisps or biscuits. They shouldn’t be considered meal replacements unless prescribed by a medical professional (in which case they’ll tell you which scientifically-proven brand you need to consume).
Research shows that combining healthy eating and regular exercise is the best way to lose weight long-term. A comprehensive review by the British Medical Journal examined 45 different weight loss studies involving almost 8000 people…
They found that efforts involving both diet and physical activity had greater weight loss benefits than diet alone. This indicates that simply drinking smoothies isn’t the answer to weight loss – you’ll get better results by exercising too.
Frequently Asked Questions
Let’s address some of the most frequently asked questions on this topic…
Smoothies can be a healthy part of a balanced overall diet. They provide the body with vitamins, minerals, fibre, and energy. But they aren’t a nutritionally balanced meal in themselves and should be consumed along with healthy meals.
Homemade smoothies can be a tasty way to incorporate fruit and veg into a balanced diet which is fundamental to weight loss. They can be a good source of fibre which helps you to feel fuller for longer so that you’re less tempted to overeat.
However, substituting multiple meals for smoothies isn’t a healthy approach to weight loss so this is best avoided. If all you fancy for breakfast is a smoothie then that’s cool, but make sure you eat lunch and dinner.
Homemade smoothies made from fruit and veg can fill you up and make you less likely to snack, which in turn can help you to lose weight. The fat burning process requires specific vitamins and minerals in order to work well so consuming smoothies can fuel you with these essential nutrients.
But drinking smoothies isn’t a solution in itself, it needs to be part of an overall lifestyle change. And don’t believe the bold claims made by supplement companies – smoothies won’t help you specifically target belly fat (or any other areas of the body).
No, consuming a pre-workout smoothie is likely to undermine your weight loss efforts. If you consume calories before working out, then you’ll just burn those calories – not the existing fat that you need to target in order to lose weight.
Sure, if you’re a marathon runner or athlete, then it’s helpful to consume calories before training. But if you’re an everyday person who just wants to lose some weight, then skip the pre-workout smoothies.
The amount of weight you can lose will depend on the amount of excess weight you have to start with. It’s all relative to your body mass and fat percentage.
Green smoothies aren’t a miracle solution but they may help people to lose weight as part of a balanced diet and active lifestyle. Benefits can include feeler fuller which reduces overeating, decreased calorie intake, reduced food cravings, and less bloating. Learn more about green smoothie benefits.
No, innocent smoothies won’t help you lose weight and can even have the opposite effect. They contain concentrated amounts of sugar which can sabotage your weight loss efforts. Preparing a homemade smoothie made from fruit and veg is a healthier option.
