My first two articles on intermittent fasting (IF) covered all the nutritional basics of the eating style and touched on how training plays into it. Now, let’s delve a little deeper by discussing what supplements should and should not be taken during a fast.

First of all, any supplements that contain calories are off limits while fasting. This includes any protein powders, pre- or post-workout drinks that contain carbs/sugar, mass gaining shakes, etc. As I mentioned in the first IF article I wrote, this should be self-explanatory, since fasting means zero calories.

With zero-calorie supplements, things get a bit more confusing for the average person. For example, branched-chain amino acids (BCAAs). Technically, BCAAs have no calories, so you often hear people say they sip on BCAAs while fasting. I get why they do this: to help preserve muscle mass while in the fasted state. But when you’re consuming BCAAs, you’re not truly fasting.

There are 20 amino acids used as the building blocks of protein, including the nine essential amino acids (leucine, isoleucine, valine, tryptophan, threonine, phenylalanine, methionine, lysine and histidine), and the 11 non-essential amino acids (arginine, serine, cysteine, glycine, proline, alanine, tyrosine, aspartic acid, asparagine, glutamic acid and glutamine).

If you consume just one of these amino acids, you’re essentially consuming protein and therefore are technically not fasting. The BCAA leucine poses a special problem with IF, and here’s why: there is emerging research linking leucine to satiety signaling in the brain, so if you’re sipping on BCAAs, the leucine may be signaling the brain that you’re currently well fed.

My suggestion is to avoid BCAAs and any of the 20 proteinogenic amino acids (those used in the building of proteins) until you’re in your feeding period. Amino acids that aren’t proteinogenic can be consumed during fasting—for example, beta-alanine, betaine, D-aspartic acid and, even though they’re not amino acids (but some people classify them as such), carnitine and creatine. These are fine to sip on during the day while fasting.

Where my JYM products are concerned, Pre JYM and Post JYM would be considered off limits during a fast because both include BCAAs. And of course, Pro JYM isn’t fasting-friendly either because it contains whole proteins and calories. However, Shred JYM and ZMA JYM can both be taken during a fast, since neither contains calories nor proteinogenic aminos. (Vita JYM, Omega JYM and Alpha JYM should all be avoided during fasting because they’re best taken with food.)