Quick, effortless and portable, meal replacements are convenient when you can’t be bothered to cook. But, that’s not the only reason why they dominate grocery store shelves. Precise quantity and nutrition partnered with a guided eating plan make meal replacements appealing for those looking to lose weight. Do they work? Let’s take a look.

Could you forgo meals and live on a solely liquid-and-bar diet?

Soylent thinks you can. As one of the latest meal replacements to hit the market, Soylent touts its products as being “engineered to provide all the protein, carbohydrates, lipids, and micronutrients that a body needs to thrive.” Each Soylent drink provides 400 calories, 20 grams of protein and 20% of daily essential micronutrients (based on a 2,000-calorie diet) — you could theoretically drink five bottles and be set for the day.

Although not intended for weight loss, there are some who look toward Soylent to lose weight and have found success. That said, it is important to note that if you’re able to create a calorie deficit, you will lose weight regardless of the meal replacement program followed.

Back to Basics: What are meal replacements?

Meal replacements, often in the form of shakes and bars, are typically made with controlled amounts of calories and nutrients. With different purposes and target markets in mind, all meal replacements are not made equally. For example, SlimFast presents itself as a weight-loss product to be taken as a low-calorie meal. Ensure and Boost market themselves as nutrient supplements to fortify the diets of those who have trouble eating enough. Soylent appeals to anyone who wants to think less about food but still get in all their essential nutrients without excess (namely sugar, salt and fat). Here’s how they differ nutritionally:

SlimFast is made high in fiber and protein for prolonged satiation. Ensure and Soylent are made to be nourishing and, thus, contain a higher calorie count and more micronutrients.

So, can meal replacements help you lose weight?

Based on a 2003 systematic review pooling data from six randomized controlled trials, the answer is a cautious yes, with major caveats. In those trials, 487 people were randomly assigned to either a partial meal replacement diet or a traditional reduced-calorie diet. Both groups lost weight after three months. At a one-year follow-up, 74% of those following diets partially supplemented with meal replacements and 33% of those following reduced-calorie diets had lost 5% or more of their initial body weight. However, the two groups ate a broad calorie range — between 800 and 1,600 calories a day — and the authors were affiliated with meal replacement companies. Hence, these results should be viewed with caution.

The Verdict

Plain and simple, relying on meal replacements misses the mark on so many levels. Meal replacements are temporary and bound to be tiresome over time; it is difficult to maintain weight loss with such a strict lifestyle. Instead, cultivate long-term healthy behaviors for a more sustainable method of weight loss.

Additionally, there is so much more to learn about nutrition, especially regarding the roles of phytonutrients and antioxidants found in food — it’s impossible to find all the nutrients our body craves in lab-formulated meal replacements. At best, they deprive us of the basic gratification of eating; at worst, they rob us of the social connection we have with others through food (Think: birthday parties and weddings).

While you may see weight-loss results, a diet solely relying on meal replacements is not the best strategy for long-term weight loss and maintenance.

Have you tried meal replacements? If so, share your thoughts below.