Liquid Diets: Is There a Healthy Way?

For the busy adult trying to stay healthy or drop a few pounds, liquid diets offer a quick and easy solution through calorie-counting and ready-to-drink bottles. But do they really provide a healthy alternative to cooking your own nutritious meals and eating responsibly?

To discuss the benefits and risks of liquid diets, we turned to Diana Sugiuchi, a registered dietitian nutritionist based in Baltimore who is also the founder of Nourish Family Nutrition and Vertical Drop Nutrition.

Liquid diets have become a pretty big health fad in recent years. What would you say started this craze?

Diana Sugiuchi: I think there are a couple reasons for this. First, people are increasingly busy with longer work hours, commutes, and obligations. 

People feel that it is time-consuming and complicated to make healthy food at home. Second, people have a genuine desire to get the right mix of nutrients and reach a healthy weight.

There is so much information and misinformation on the Internet about what is healthy and the best ways to lose weight, and much of it conflicts. 

People are confused. Liquid diets are nutritionally analyzed, portion controlled, and simple. And because they are manufactured by companies, there is a sense that they are guaranteed to be healthy.

What are the most popular liquid diets on the market?

Sugiuchi: There are the weight loss standbys, like Slim-Fast and Herbalife. Some liquid supplements that used to be used mostly in hospitals to help people gain or maintain weight when ill, like Ensure, are now marketing themselves as helping healthy people build muscle [and helping] picky children get in all their nutrients. Shakeology is one I am seeing more of. The one that has been receiving the most buzz lately is Soylent, which is marketed as a liquid diet that can be used in place of food.

What are most people looking for when they start a liquid diet?

Sugiuchi: People are looking for something easy that will help them to be healthy or lose weight. I believe that people want a guarantee that what they are putting in their mouth is healthy and something they should be eating, and these liquid diets are offering those guarantees, whether they are proven or not.

Do certain people benefit more from liquid diets than others?

Sugiuchi: People who cannot chew or swallow food benefit most from liquid diets. If you are looking to jumpstart weight loss, a couple days on a liquid diet will not hurt you, but aiming to do it for the long term will not lead to success.

Are liquid diets more effective than other kinds of diets?

Sugiuchi: Any diet where you are taking in fewer calories than you are burning will result in weight loss. But if you haven’t made lifestyle changes, you will not keep the weight off.

What are the benefits of liquid diets?

Sugiuchi: The convenience and regulating calories.

And what about the risks?

Sugiuchi: These supplements are not regulated like food. Some of them have harmful ingredients that are not listed on the label, such as lead. When used long term, nutritional deficiencies could occur if the supplement does not have all of the nutrients necessary or if the nutrients that it claims to have are not really in there. Our bodies were designed to chew and digest whole food, and if there is not a good reason why you cannot do this, a liquid diet is risky. If you don’t make healthy changes in your diet for the long term, you will not be successful with weight loss or sustained healthy eating.

What difference is there in the way the body absorbs calories through drinking versus eating whole foods?

Sugiuchi: Our bodies don’t register the calories that we drink in the same way that [they recognize] the calories that we eat. For example, if you drink something that has 250 calories, you will likely not feel as satisfied as if you ate something, like a sandwich, that had 250 calories. This can lead to taking in more calories and feelings of hunger even when you have had enough calories.

Why does the body not register calories the same way? Is there a way around this, or should those trying a liquid diet just be cautious of these risks?

Sugiuchi: Eating involves much more than just ingesting calories. The aroma of food, the act of chewing, and swallowing all play a part in how satisfied we feel after a meal. A liquid diet offers none of these benefits.

So which liquid diets are healthy? And how long should one stay on the diet?

Sugiuchi: I would not recommend anyone to stay on a liquid diet for more than a few days. Based on experience, most people will not want to stay on a liquid diet for any longer than this! If you are going to choose a supplement for a liquid diet, look for one that has 100 percent of your recommended vitamins and minerals, at least 60 grams of protein per day, and 25 grams of fiber per day, as well as healthy sources of fat.

Which liquid diets definitely aren't healthy?

Sugiuchi: Any liquid that has added caffeine or herbs. These can have interactions, and the substances may not actually be what they say they are.

What questions should a person ask a nutritionist when considering going on a liquid diet?

Sugiuchi: Ask a nutritionist if the supplement you are considering will meet 100 percent of your nutrition needs. Look for added caffeine or herbs that don’t need to be in there. You should also ask if this is something that would be helpful to you. And you always want to make sure that your supplement has been verified to be safe by an independent source outside the supplement manufacturer, such as Consumer Lab.

What about juice cleanses? How effective are they? And what are the benefits and risks?

Sugiuchi: Juice cleanses can backfire. Not only are these low in calories, but they are very low in protein. Because of this, much of the weight loss comes from loss of water and muscle, not from fat loss, and the weight is regained when normal diet is resumed.

There is nothing magical about juice that would help our bodies detox any better than a well-rounded diet focused on a variety of less-processed foods. And the very low calories can actually cause metabolism to slow down, which can make it harder to lose weight. Just like any liquid diet, if it helps you to make a break with poor eating habits and you are truly committed to long-term diet change, a couple days on a juice cleanse likely won’t hurt, but it certainly isn’t necessary.

Joe Bowman

healthline