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You were planning to drop a few pounds this spring, but you never got around to eating less and exercising more on a regular basis. So, with summertime already here, you are considering how to quickly shed that extra weight… Could diet shakes be the key to a slimmer you? Maybe, but is it really that simple? It’s very common for people to be tempted to stray from their usual sensible diet plan and instead try something a little more extreme to quickly shift those pounds. In this week’s article learn the truth about the most common meal replacement diet; the diet shakes.

What’s the theory?

In order to lose weight you need to take in fewer calories than your body needs. When this happens, the body uses its fat stores to provide you with the extra energy to function properly (see here). In the long term, this means fat loss and therefore weight loss. Quite simply, meal replacement products provide around 1,200-1,400 calories each day and they offer a way to help you control your calorie intake.

Diet Shakes Pros and Cons

As nutritionist I would advise people to lose weight on a balanced, low-fat diet that includes lots of fruits and vegetables because whole foods provide a much better balance of nutrients than meal replacements. Moreover, using real foods forces you to make choices that help you maintain weight loss in the long run. However, it’s true that this approach doesn’t work best for everyone, so sometimes I would recommend liquid meal replacements as part of a healthy eating plan.

According to recent research however, diet shakes, also called meal replacements, were just as effective for producing weight loss when compared with conventional, structured weight loss diets. Diet shakes are particularly useful for jump-starting weight loss. Keep in mind that a healthy weight loss should be limited to no more than about 2 pounds a week (almost 1 kg). As with meal replacement bars or low-calorie entrees, diet shakes help you keep tight control on calories. For example, they are particularly useful for people who can’t lose weight when they exceed their calorie quota even by a little. Of course, diet shakes of any type won’t work toward weight loss unless you eat fewer calories than you burn every day. To use diet shakes and meal replacement beverages most effectively, determine a calorie allowance for weight loss. You may be tempted to limit yourself to a daily intake of 1,200 calories for fast results, but 1,500 calories may help you stick with your eating changes longer. Be sure to include exercise, which aids weight control and promotes good health.

Are diet shakes the simplest way to diet?

Diet shakes and other meal replacements are useful when you lack the time or motivation to prepare balanced meals. They also help when you just don’t want to think too hard about what to eat to lose weight. The makers of some ready-to-drink meals recommend sipping one each for breakfast and lunch, and eating a sensible or healthy low-fat dinner, keeping food preparation to a minimum. You may make it through the day on automatic pilot by relying on diet shakes, but you can’t completely escape thinking about calories and other nutrients. Even when diet shakes stand in for two out of three meals, you still need to interpret “sensible” and “healthy low-fat” when choosing your dinner.

Probably the most difficult part of following a meal replacement diet plan is dinner. The reason is that many people eat at night to relieve tension from the day. Going overboard at dinner (and during the night) can effectively wipe out the calorie deficits that contribute to weight loss. For example limiting dinner to 100-150 grams of cooked lean meat; a medium baked or sweet potato or a 1/2-cup cooked rice or pasta; and a cup of cooked broccoli or other vegetable seems a sensible way of getting nutrients without excess calories. Another option for keeping evening calorie consumption in check: Eat more at breakfast and lunch and choose a diet shake and salad for dinner instead of a full meal, always working within your calorie allowance. Additionally, try to include fruit as snacks during the day to reduce the chance of overeating at dinnertime.

Are meal replacement products healthy?

By law, meal replacement products must provide the recommended amount of nutrients needed for good health and their composition must conform to certain standards defined by a European Directive. According to the guidelines, meal replacement products must contain between 200 and 400 calories, at least 25 percent protein, 23 vitamins and minerals and 5-6 grams of fibre. Ultimately, meal replacement products are not designed to be the only source of nutrition.

Are there any disadvantages?

One of the main problems with the research to date is that no large long-term trials have been carried out in the UK; the majority of research has been based in the USA and Germany. Meanwhile, few trials have taken place using meal replacements in ‘real-life’ situations. Furthermore, most studies have used meal replacements as part of a comprehensive programme, which includes support and dietary advice from health professionals, but what happens when people buy and use meal replacement products on their own? Finally, most studies have involved people who are overweight or obese but few have studied normal weight people with a Body Mass Index of 20-24.9, who simply want to lose a small amount of weight.

The main problem with meal replacement diets is that on their own, they do little to educate people about their eating habits. While replacing high-calorie breakfasts and lunches with a shake will almost certainly result in weight loss, returning to poor eating habits once you stop taking the products means you will almost certainly put the weight back on again.

However, thanks to a number of studies supporting their use, several major health organisations such as the National Obesity Forum, the British Dietetic Association and Dietitians in Obesity Management UK now suggest meal replacements are a suitable option for some people. However, they also say this is just one of a range of possible dietary treatments to help people lose weight and recommend that additional support and advice needs to be given so that people learn to change the poor eating habits that helped them pile on the extra weight in the first place. Keep in mind that you shouldn’t stay on a strict diet shake plan for more than 3-4 months.


Diet shakes are not the magic pill for weight loss. Used correctly, they can help you get started on weight loss or help you maintain a healthier weight. But to lose weight or even to eat well while maintaining a healthy weight, you must be committed and consistent with your eating and exercise habits.

If you’re considering trying a meal replacement plan, have a look at the Nutrition section of our website and browse through the many different products on offer!

By Kleio Bathrellou
Associate Nutritionist

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