Does HMB Break a Fast?

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Intermittent fasting is a great diet for health, weight loss, blood sugar management, and more. But a common worry, especially among those lifting weights and trying to gain muscle is the risk to lose muscle mass due to fasting. Most protein supplements, including BCAAs, break a fast because they cause an insulin reaction. But what about HMB, a less-known supplement that is meant to slow down muscle breakdown. Does HMB break a fast?

 HMB does not cause an insulin reaction, so if you’re fasting for fat loss or blood sugar management, this is a safe supplement. If you’re interested in autophagy, the answer isn’t so straightforward. Several studies suggest HMB inhibits autophagy, though many consider this study is not extensive enough to provide a definitive answer.

Let’s take a closer look at HMB, its effects on fasting, its benefits, and side effects.


Does HMB break a fast?

Beta-hydroxy-beta-methyl butyrate, in short HMB, is a chemical produced by the body in response to the amino acid leucine. As a supplement, it is used to slow down muscle breakdown and it is especially popular among those who do long water fasts to prevent the loss of muscle mass.

HMB does not cause an insulin reaction, so it won’t break a fast meant for fat loss or blood sugar management. If you’re fasting for autophagy, studies show HMB is not an ideal supplement because it inhibits it. There are no official studies to say how taking this supplement affect gut rest, so you should assume there’s a risk it will stimulate the gut and break this type of fast as well.

In other words, you can safely take HMB during your fast if you’re fasting to lose fat or manage blood sugar. In any other case, you should leave your supplement for your eating window.


When should I use HMB when exercising in the morning?morning workout

The recommended dose of HMB is about 3 grams at least one hour before an intense workout. HMB doesn’t immediately become available in the body, so to benefit from its boost of energy, you need to give it enough time to act.

If you’re not exercising in a fasted state and take your HMB with food, or immediately after, you should allow about 2 hours between the supplementation and the workout.

For more experienced athletes, a loading dose is recommended two weeks before switching to a new workout routine. This dose consists of 1 gram 3 times a day for two weeks before starting the new exercise routine.


Will taking HMB during a fast make me lose muscle?muscle

No, HMB has the completely opposite effect. HMB is made by the body as a response to leucine. This amino acid is known for preventing muscle loss, soreness, and fatigue. What you might not know is that it is actually the HMB that does most of this work. That’s why bodybuilders and athletes who fast often choose to supplement with HMB to prevent losing their muscle.


Benefits of HMB

We already talked about how HMB helps prevent or slow down muscle breakdown. But that is not its only benefit for people who fast.

HMB provides a boost of energy that can be very helpful if you like to workout in a fasted state. It’s also helpful for those who go through longer fasts when insulin levels lower considerably and with them, energy levels might tank as well. HMB increases fat oxidation, meaning, in the absence of insulin, it will help you get energy from your fat storage. And here’s where you get a bonus effect: by using fat for energy, HMB could help you lose weight faster.

Another great benefit for people who do intermittent fasting is that HMB helps lower cortisol. Why is that important? Because intermittent fasting can actually increase cortisol levels. Also known as the stress hormone, cortisol helps us react to danger. The problem is, in this day and age, we are prone to too much cortisol.

Our body doesn’t really know the difference between the type of stress when you’re running from your life and when you’re sitting in your car, annoyed at the traffic because it will make you late for work. The body only perceives a high stressor and helps raise cortisol which should helps you survive. But because you’re not running for your life, you’re not using cortisol, so you get an excess of it.

Intermittent fasting is also known to raise cortisol levels, especially in the case of long fasts. So a supplement that helps manage the stress hormone is going to be extremely helpful.

Other benefits include better aerobic endurance, faster recovery time, and increased strength. In other words, HMB is very helpful for athletes and those who do intense workouts regularly.


Side effects of HMB

In the recommended dose of up to 3 grams per day, there are no notable side effects to taking HMB. If you’re pregnant or breastfeeding you should avoid this supplement, as there aren’t enough studies regarding its safety in these cases. And, of course, if you have any symptoms that you believe are due to HMB, stop taking it immediately and see how you feel.


What is the best HMB supplement product?

HMB is one of the more expensive supplements. But instead of buying a low-quality one, I really recommend investing into a good, high-quality product. I recommend MET-Rx HMB 1000 from Amazon. Here are the key points:

  • 130mg calcium/capsule
  • 90 capsules
  • Provides muscle & strength support
  • Prevents muscle breakdown


The bottom line

Does HMB break a fast? If you’re fasting for fat loss or blood sugar management, HMB is safe to take. It does not cause an insulin response, so it will not break your fast. For autophagy, however, HMB is not an ideal supplement.

It is mostly recommended for those who are worried fasting may lead to muscle loss. Whether you’re fasting for extended periods, or are working towards a muscle-building goal, HMB could help slow down muscle breakdown that naturally happens during a fast. It is best to take it about an hour before an intense workout to get the maximum benefits. Those who do not work out in a fasted state and therefore take HMB during or after a meal should take it at least 2 hours before they exercise.

HMB is a safe supplement, with no notable side effects recorded, but if you have any worrying symptoms, take a break from it to see how you feel.

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