Do Meal Replacement Shakes Really Work for Weight Loss?
David Heber, M.D., Ph.D., FACP, FASN – Chairman, Herbalife Nutrition Institute January 23, 2024
Losing weight is not always easy. Given the hectic pace of modern life, people have turned to diets or dubious weight-loss schemes. Meal replacements, along with diet and exercise, offer a better alternative and an effective solution to weight loss and weight management.
The benefits are based on the convenience of meal replacements, their ability to satisfy hunger and providing nutrients that your body needs every day.
Let’s dig deeper into why meal replacements work better than typical calorie-restricted diets, according to science and research.
The Science Behind Meal Replacement Products
There’s nothing magical about meal replacements, and they’re not as bland or boring as food replacements in science fiction may suggest. Today, there are a hundred or more ways to prepare meal replacement shakes that taste great and fill you up for hours.
There are three science-based reasons why meal replacements work well for weight management:
- Protein and Glycemic Index
- Nutrient Density
- Behavioral Changes
Protein and Glycemic Index
Protein is the most satiating macronutrient – meaning it controls hunger for longer than carbohydrates or fats. Getting the right amount of protein to control hunger at every meal every day is key to achieving and maintaining a healthy body weight. Plant- and animal-based proteins tend to be some of the main ingredients in many meal replacements.
Meal replacement shakes also have a low glycemic index. The glycemic index (GI) is a way to measure how quickly and how much a food causes blood sugar levels to rise. When you consume foods with a high GI, your blood sugar will spike and then fall sharply, promoting lethargy and hunger.
However, a meal replacement shake, like other foods with a low glycemic index, releases sugar into the blood more slowly – providing another way for meal replacements to help control hunger.
Whenever you consume foods that have a low glycemic index, such as fruits, vegetables, whole grains and meal replacements, your body digests them more slowly than simple carbohydrates and sugar in snack foods.
As a result, there is a slower rise in blood sugar. Protein, which helps to lower the glycemic index, has a clinically proven effect on controlling hunger. Getting the right amount of protein is key to the effectiveness of meal replacements. Meal replacements that have a low glycemic index can curb appetite despite their lower calories compared to typical meals.
It’s important to note, however, that a low GI doesn’t necessarily mean a food is high in nutrients. This is why the next concept is so important.
Nutrient density refers to the ratio of nutrients (proteins, carbs, fats, and vitamins and minerals) to calories in a food. A food with low nutrient density provides lots of calories, fat and sugar with few essential nutrients. Cookies, cakes, pasta and sugary soft drinks fall into this category.
High nutrient density foods provide lots of nutrients per calorie and include fruits, vegetables, lean meats and fish, and meal replacements. They can also help you feel full longer.
In other words, nutrient density is a measure of how much nutrition you get per serving or per calorie eaten. Most meal replacement products may deliver vitamins and minerals to make them nutrient dense.
Meal replacements promote a high-quality diet by being nutrient dense and having a low GI. When combined with resistance exercise, meal replacements can also help promote lean body mass to maintain or build lean muscle and support fat loss.
In fact, a trial was conducted to investigate the effect of a high-protein partial meal replacement (HPMR) diet on nutrient intake in overweight and obese people. Based on the results, the HPMR diet led to an overall improvement in diet quality over the course of the study. Significant decreases in fat and cholesterol intake and substantial increases in protein and fiber intake were observed at all time points.
Dietary intake of all micronutrients tested, including nutrients of U.S. public health concern (vitamin D, calcium and potassium) increased significantly at all time points from the baseline, and sodium intake significantly decreased.
Considering that those who are overweight or obese are likely struggling to consume a nutrient-balanced diet, the HPMR diet may be an effective strategy to enhance the overall nutrition quality of their diet. The HPMR diet could be incorporated into a healthy lifestyle program that includes healthy eating and exercise for those at risk for macronutrient and micronutrient deficiencies.
Aside from the above nutritional considerations, meal replacements simplify weight management by allowing you to focus on controlling foods in one or two meals per day. The behavioral advantages of an HPMR diet are as key as the nutritional advantages of typical or fad diets.
The Medicine Department of the University of Ulm, Germany, carried out a four-year study of obese patients (who were not taking Herbalife products). Researchers identified six specific reasons why meal replacement diets worked so effectively for weight loss.
These reasons include:
Lack of time to prepare healthy meals is one of the biggest barriers to losing weight. Meal replacements make it easier to plan meals.
2. Increased compliance
Meal replacements reduce barriers to dietary adherence, such as the temptation to indulge in unhealthy foods.
3. Regular eating pattern
Repetition and routine are key in a weight-loss or weight-maintenance journey. Eating at regular times throughout the day and avoiding long periods of time between each meal positively affect your energy level and hunger feeling.
4. Accuracy of calorie estimation
Dietitians typically advise consuming a certain number of calories throughout the day, depending on your health goals. Meal replacements – when prepared as suggested – are an easy, precise way to keep track of how many calories you are consuming.
5. Quality of food consumed
Cutting back on calories can make it difficult to obtain the required nutrients. Meal replacements are often fortified with vitamins, minerals, protein and fiber, which help avoid a nutrient gap.
6. Positively affects self-monitoring
Recording dietary intake helps people become aware of their current food-related behaviors. Tracking meal replacements is easy, making self-awareness of target behaviors and outcomes easier.
Evidence Why Meal Replacements Are Effective
In 2018, researchers from the University of Oxford published a systematic review and meta-analysis of meal replacements for weight management. They reviewed 14 studies that compared the effect of weight-loss interventions that incorporated meal replacements to those of alternative interventions.
They concluded that meal replacements are superior to usual diet and calorie restriction.
New Findings From the Meta-Analysis
According to the study, participants assigned to a meal replacement diet lost an additional 1.44 kilograms (3.17 pounds) in one year compared to a diet-only approach.
The researchers also observed that participants in the meal replacement group who joined behavioral weight-loss programs to enhance their effect had a greater weight loss of 6.13 kilograms (13.51 pounds) within the group.*
This finding underlines the value of social support, as these types of programs make it easier for people to adhere to a reduced energy diet. The structure and external control associated with these programs may also promote adherence.
Someone simply purchasing meal replacements from a grocery store can easily grow tired of the same flavor and give up, whereas a behavioral program or supportive community will lead to greater adherence.
Meal Replacements for Clinical Use
In many countries today, the clinical recommendations for the treatment of obesity advise that individuals attempting weight loss should aim for an energy deficit of 500 to 1,000 calories. Unfortunately, few clinicians encourage meal replacements as tools to help patients achieve this deficit.
The meta-analysis provides new evidence to inform clinical guidelines, especially when it comes to obesity. The use of meal replacements should be promoted as an effective dietary strategy for weight loss since meal replacements are proven to be effective and easily available without a prescription. However, it’s important to note that, as with any changes in your diet and physical activity levels, individuals should always consult their physician before engaging in any weight-loss journey.
Meal replacements for weight control have also been reviewed by the European Food Safety Authority (EFSA). The Panel on Dietetic Products, Nutrition and Allergies was commissioned to provide a scientific opinion regarding the weight-loss claims related to meal replacements.
In their paper, they recognized the following:
- Weight loss achieved with meal replacement products was significantly greater than with conventional energy-restricted diets prescribed with the same calorie content.
- When weight-loss strategies were equally effective, the intensity of intervention required was three times higher for the conventional energy-restricted diets than for meal replacements.
Case in Point: A Review of Herbalife Meal Replacements
Not all meal replacements are the same. Quality is a key differentiating factor, especially when it comes to products that are commercially available.
In 2020, independent researchers investigated the efficacy and safety of Herbalife® products used as high-protein meal replacements for weight management. While the study was funded by the company, we had no control over study execution or manuscript preparation, including data analysis, data interpretation or manuscript drafting.
In their meta-analysis, they reviewed randomized controlled trials of the company’s high-protein (HP) products used as a meal replacement (MR), published through July 2019 in peer-reviewed journals. The researchers consolidated data from nine studies, which included 934 participants: 463 in treatment groups and 471 in control groups.
Ultimately, they found that participants who consumed Herbalife® HP products experienced significantly larger decreases in body weight, body mass index and fat mass – compared to the individuals consuming control diets.
Conclusion: High-Protein Meal Replacements Can Be Effective for Weight Loss
In summary, these studies show that meal replacement shakes work better than self-directed weight-loss attempts. While popular diets might work for short-term weight loss, in the long run, adherence will be an issue.
If you’re looking to achieve and maintain a healthy body weight over the long term with a partial meal replacement diet, it’s important to pair it with balanced nutrition and a healthy, active lifestyle. Social support also goes a long way, and it can be helpful to find a motivating community to help with your program.