Selecting a diet plan that's right for you may take several periods of trial and error. Replacing one or two meals per day with a meal replacement drink may help you lose weight initially, but there are a few factors you should be aware of. Talk with a healthcare provider, such as a registered dietitian, to ensure that replacing meals with diet drinks is a good fit for you.
Fatigue from Inadequate Calories
Meal replacement drinks provide around 200 calories for each serving. If you replace two meals with these diet beverages and then eat one meal that contains 600 calories, you only consume about 1,000 calories for the entire day. If you're used to following a 2,000-calorie diet, drastically cutting your calories in half with meal replacement drinks can cause you to feel tired and fatigued throughout the day. This may not be enough calories to sustain your activity level, especially if you have a physically demanding job or if you routinely work out. Adapt to the diet by replacing only one meal with a meal replacement drink in the beginning to allow your body to adjust to the sudden decrease in calories.
Effect on Digestive Health
Your digestive tract may suffer by replacing a couple meals a day with a meal replacement drink. Women need 26 grams of fiber throughout the day and men need as much as 38 grams, the Linus Pauling Institute reports. These types of drinks typically don't contain much fiber, which makes it hard to reach your intake recommendation. You need both soluble and insoluble fiber to keep food moving through your gut and to keep you regular. Replacing two out of three meals with a meal replacement drink may limit the type of fiber you get in your diet. You may suffer from irregularity, diarrhea or constipation by having inadequate fiber in your diet.
Effects on Satiety
Satiety is the way you feel when you are full. Fiber in your diet helps keep you full, improving satiety, since it sits in your digestive tract for awhile, slowing digestion and creating bulk. This can help keep you feel full between meals so you're less likely to snack. Additionally, high-fiber foods take longer for you to chew, allowing your body to register that it is full. This can help your weight loss efforts since you probably won't have a desire to eat as much during a meal. Because you don't get the chewing benefit from having a meal replacement drink, you may consume it quickly, reducing your satiety and causing you to feel hungry again shortly after.
Effects on Nutrient Intake
One of the greatest benefits of meal replacement drinks is that they are full of vitamins and minerals. This allows you to monitor exactly how much of each nutrient you consume throughout the day. They are a convenient way to sneak in beneficial vitamins and minerals, without having to consume an array of fruits, vegetables and whole-grains. Meal replacement drinks are also typically high in protein. You can get all of these benefits while consuming only a few grams of fat and minimal calories. However, because food naturally contains thousands of other beneficial compounds, in addition to vitamins and minerals, meal replacement shakes might not offer the same benefits as unprocessed and healthful foods.