Are Liquid Diets for Weight Loss Safe and Effective?

Liquid diets for weight loss are hugely popular, with options like the Master Cleanse, high protein liquid diet shakes or the many juice fasts that exist on the market. There are a lot of claims around these diets about how they might help with detoxing various organs or are the key to fast weight loss, but are they really safe and effective? Should you be going on a liquid-only diet in order to drop pounds or should you avoid liquid diets?

Are Liquid Diets Safe?

First, let’s start with the handful of benefits of liquid diets. Here are a few potential healthy aspects of liquid diets for weight loss:

  • Increased fluid intake. Staying hydrated can increase your metabolism by up to 24%.1 Most of us are mildly dehydrated because we don’t drink enough water or eat enough foods high in water, like fruits and vegetables. The 8 glasses a day that many of us believe is enough actually doesn’t meet our hydration needs.

    Men need approximately 15 cups of water per day, while women need about 11 cups.2 You need even more if you are exercising or live in a hot climate. A liquid diet can help you to increase your fluid intake to improve hydration.

  • More veggies and fruits. For people who struggle to eat enough fruits and veggies to hit the target of 5-9 servings a day, a juice-based liquid diet can be a great way to increase plant intake. You can even throw fruits and vegetables into a protein shake. Mixing fruits and veggies into your daily smoothies and shakes ensures you get more of the minerals, vitamins, fiber and antioxidants than you might otherwise.

  • Quick weight loss. If you go on a liquid diet, there’s a very real chance you’ll lose weight really quickly. Although this might be exciting, this very fast weight loss isn’t a good thing and will likely cause you to gain it back even faster once you go back to eating normally again.

So, yes, there are a few potentially healthy aspects of liquid diets. However, there are many negative aspects, and may want to take the following downsides into account before committing to one: 

  • Fatigue and lack of energy. Most liquid diets do not provide enough calories to meet daily needs. Not eating enough calories means your body has less energy available to use for day-to-day activities. If you try to exercise, you may feel dizzy or lightheaded from the lack of calories.  You will likely end up getting tired more easily and you will feel a bit more “blah” than usual because you’re not consuming enough calories.
  • Weight loss won’t last. When you initially go on the liquid diet for weight loss, you see a decrease of a few pounds the first week or two. This is due to fluid loss from all the liquids you are drinking and lack of calories. Most of this weight loss is fluid, not actual fat.

    After a few weeks your body will adapt to its circumstances, so low calorie intake will cause a slowdown in your metabolism. Basically, your body moves into starvation mode; your body will stop needing as many calories, so you will have to stick with a low calorie diet forever or else you will gain weight back.

    The body will also start to eat up your muscles for energy, slowing your metabolism even more. With a slower metabolism, the weight loss will eventually stop. You may start to gain weight, even with an extremely low calorie intake. Liquid diets, even high protein liquid diets designed to maintain muscle mass, can slow down metabolism when used long-term.
  • Digestive problems. Your body needs solid food, especially fiber and fats, for healthy digestion. Changing your diet to a liquid-heavy one may cause some changes to your digestive tract as well. Diarrhea is a possible side effect of a liquids-only diet, as there is more water than your body is able to absorb and process. You may end up missing out on vital nutrients because the liquids are moving through your intestines too quickly.

  • Nutrient deficiencies. When you follow a liquid-only diet, you cut back on many critical nutrients found in solid foods. Unless you are very careful to include plenty of protein and fats in your liquid diet plan, you may find yourself lacking those important macronutrients. Of course there are some high protein liquid diets out there that try to prevent this issue, and some of these may provide the minimum amount of protein you need, but they still might not be adequate long-term.

    Micronutrients may also be lacking, particularly minerals like iron or zinc, which increases the risk of nutrient deficiency. In the long-term, if you are not careful, a liquid diet can lead to vitamin and mineral deficiencies.

As you can see, liquid diets for weight loss have some concerns associated with them. Although there are a few potential benefits, they are not an ideal long-term strategy for sustainable weight loss.

What is a Good Liquid Diet?

Why does the liquid diet trend persist? There are a few principles of liquid diets that can work. You can apply some of these to your own diet to promote weight loss and health without entirely eliminating solid foods.

First, there is nothing wrong with increasing fluid intake, as you would on a liquid diet. More liquid is always good for you, so increasing your liquid intake will lead to better health and speed up your metabolism. Drinking more water, tea and veggie-heavy juices can help promote weight loss. Just because liquids-only diets aren’t great, that doesn’t mean you shouldn’t find ways to get more fluids in your daily life.

You may also consider replacing one meal a day with a protein shake, veggie juice or smoothie. This option can help you cut back on calories and get in a few extra nutrients, while still allowing you to eat solid food for the other two meals. Using a high protein shake is probably your best bet for a meal replacement. This way you give your muscles the protein they need to keep your metabolism moving and it helps you feel full longer.

It’s vital that you understand that long-term low calorie liquid diets are not really the easy fix they’ve been made out to be, and they may lead to serious health problems if you continue them for more than a few weeks at a time. Instead of going on a crash diet like this, use the two tips above to help you lose weight the safe, healthy and sustainable way!