Weight Cutting: What Making Weight Does to Your Body

Making weight is the part of fighting that happens before anyone throws a punch. Most of what gets said about it is gym lore: drink a gallon a day, then stop, sit in the sauna, spit in a towel. What's missing is data on what actually happens inside a fighter doing it.

A 2020 study in Sports supplied some, and the useful thing about it is that the cut was done right, so the numbers are a best case, not a horror story.

The setup

Twenty-one high-level Italian Muay Thai fighters, eight of them women, went through a supervised three-day rapid weight loss: about a 1,000-calorie daily deficit, carbohydrates dropped low, protein kept high, plus targeted supplements. Then an eight-hour refeed to load back up before competition. Blood, hormones, and body composition were measured at each stage.

This is the cut a nutritionist would design. No dehydration stunts, no last-minute sauna gambit. Keep that in mind, because it's the floor, not the ceiling, of how rough making weight gets.

What came off, and what came back

The fighters lost about 4.1% of their body mass over the three days (3.5% for the women and 4.4% for the men). After the eight-hour refeed they put most of it back, landing near their starting weight by competition.

So far that reads like a clean process: down for the scale, back up for the fight. The body-composition markers agreed. A measure of cellular health (phase angle) dipped during the cut and then fully recovered. Kidney markers rose but stayed inside the normal range, with no sign of actual kidney injury. Hydration recovered. On the surface, a supervised cut looks survivable, because it is.

The cost that didn't bounce back

The hormones tell a different story.

In the men, testosterone fell significantly after the weight loss, with a large effect, and then kept falling even after refeeding (the opposite of the body weight, which recovered). Thyroid hormone (TSH) dropped during the cut before rebounding afterward. Blood glucose climbed throughout.

The authors didn't hedge about it: the disruption to the hormonal profile was, in their framing, essentially inevitable. You can protect the kidneys and rehydrate the cells, but you can't run a steep energy deficit through an endocrine system and expect it to shrug. And this was three days. The fighters who cut for a week or more, repeatedly, across a career are running that deficit far more often.

How to make weight without wrecking yourself

The study's own guidance is concrete:

• Keep a cut to about 5% of body mass or less. The fighters who go for 8–10% are in different, worse territory.
• Do it no more than two or three times a year. The damage is about repetition as much as depth.
• Female athletes need extra caution, particularly anyone with menstrual irregularities, since the hormonal cost lands differently.
• Make the cut gradual, fueled, and supervised, not a dehydration sprint. The reason this study's markers stayed safe is that it was planned, not crash-induced.

The caveats: this was 21 fighters, one cut, no comparison group, and the supplements were supplied by LightFlow Technology; the authors declared no external funding or conflicts. It's a careful look at a single careful cut, not the last word. But the direction is clear enough to act on: making weight is a real physiological event, the scale lies about how recovered you are, and the smart cut is the small, rare, well-fed one.

If you're chasing a number on the scale to fight, it's worth asking the same question this blog keeps asking about head contact and sparring volume: are you sure the risk you're taking is the one you think you're taking?

The research

• Cannataro R, Cione E, Gallelli L, Marzullo N, Bonilla DA. Acute effects of supervised making weight on health markers, hormones and body composition in Muay Thai fighters. Sports, 2020;8(10):137. doi:10.3390/sports8100137