About the author
Peter Miller is the founder of Condition Nutrition and a combat sports nutritionist who has supported 20 world champions across the UFC, ONE Championship, Professional Fighters League, Cage Warriors, WBC Muay Thai and Olympic boxing. He holds a Master’s degree in Sports and Exercise Science (University of Chester) and an ISSN Diploma in Sports Nutrition (Middlesex University), and has been described by the South China Morning Post as ONE Championship’s leading fight-week nutritionist.
Read full credentials and athlete track record
Health and safety notice: This article is educational and is not a substitute for individual medical advice. Rapid weight cutting, extreme dehydration and water loading carry real risks, including dangerous electrolyte imbalance. People have died cutting weight. Always work with a qualified professional and consult a doctor before manipulating body weight or fluids.
Direct answer
How do you cut weight for a fight without losing power?
Lose most of the weight gradually as fat across fight camp, aiming to be around 8% above your fight weight one week out. In fight week, drop the rest by reducing carbohydrates, fibre and salt, with short water loading only if needed, rather than crash dehydration. Then rehydrate and refuel properly after the weigh-in. As Peter Miller puts it, the cut is “a marathon not a sprint”.
Watch the full interview: Combat Sport Nutrition Expert Pete Miller — Kickin’ It With Liam Harrison #32
Contents
1. Why old-school weight cutting is trial and error
2. Start with body composition, not an arbitrary weight
3. The four phases of a fight camp weight cut
4. The three fight-week levers: carbs, fibre and salt
5. Water loading: three days, not a fortnight
6. Rehydration and the post-weigh-in refuel
7. How Condition Nutrition approaches a fight week
1. Why old-school weight cutting is trial and error
Combat sports nutrition research is young. As Peter explained to Liam Harrison, if you search for fuelling guidance for a footballer or a marathon runner you find decades of studies, but for fighters there has historically been very little. The result is that most weight-making advice has been handed down from coach to coach rather than tested.
That is how you end up with the horror stories: fighters weighing in at a fast-food restaurant, eating a chocolate bar instead of a fuelling strategy, or losing several kilos in a sauna the night before. Liam was candid that for years he was “just winging it”, and that doing it blind can knock a large chunk off your performance on the night.
2. Start with body composition, not an arbitrary weight
The first question Peter asks a new fighter is why they fight at their chosen weight. The answer is often simply that a coach told them to, with no physiological rationale behind it. Many fighters compete in the wrong weight class: too big and lean for it, which forces a brutal cut, or carrying too little body fat to draw the weight from safely.
This is why a body composition assessment comes first. Measuring fat mass against lean mass shows how much can be lost safely, and whether the fighter can make that weight repeatedly across a career rather than destroying themselves once. As Peter says, if you are “too lean for your weight class”, the weight has to come from somewhere, and that somewhere is dangerous dehydration. A DEXA scan is the most accurate option, followed by skinfold calipers taken by a trained technician, with in-body machines giving a rougher range.
3. The four phases of a fight camp weight cut
Peter breaks a fight camp into four phases. The structure is what keeps the cut controlled rather than chaotic.
| Phase | What happens | Goal |
| 1. Chronic weight loss | Roughly 8 to 10 weeks out. Gradual loss of body mass through fat, fuelled by training. | Reach about 8% above fight weight by one week out, losing fat not muscle. |
| 2. Acute weight loss (fight week) | The final days. Reduce carbohydrates, fibre and salt, with optional short water loading. | Drop the remaining few per cent safely, without crash dehydration. |
| 3. Post-weigh-in refuel | Restore fluids first, then fast-digesting carbohydrates. | Rehydrate and reload glycogen before the first bell. |
| 4. Fight day nutrition | Familiar, carbohydrate-based meals the fighter already trusts. | Arrive fuelled, settled and ready to perform. |
Table: the four-phase fight camp structure described by Peter Miller on the podcast.
The key number is the 8% target. If the chronic phase is done well and the fighter is roughly 8% above fight weight a week out, fight week becomes manageable. If they arrive at 10 to 12% because they dieted too aggressively or fight in the wrong class, the acute cut becomes far more dangerous. As Liam put it, get fight week right and the weight “just dropped off” without ever going hungry.
4. The three fight-week levers: carbs, fibre and salt
Fight week is where the acute weight comes off, and Peter uses three levers rather than the sauna. The reason they work is that you must keep eating properly right up to fight week; strip carbs out three weeks early and you have nothing left to manipulate.
- Carbohydrates. Every gram of stored glycogen holds roughly three grams of water. Reducing carbohydrates to around 30 to 50 grams a day for five to seven days can lower body mass by around two to three per cent.
- Fibre. Fibre sits undigested in the gut. Cutting it to under about 10 grams a day clears that residue and can take off another one to two per cent. This is the accurate version of the “low-residue” idea: it reduces gut content, it is not a magic drop.
- Salt. Salt holds water. Cutting it during fight week releases that water. Liam described going from 70kg to 68kg in two days largely by changing one salted meal.
Done together, these three levers handle the fight-week percentage so the fighter is not forced into a desperate water cut to find weight that simply is not there.
5. Water loading: three days, not a fortnight
Water loading is the most abused part of fight week. Peter has heard of fighters drinking 14 litres a day for two weeks, which is both unnecessary and dangerous. In a study he referenced, grapplers on a fight-week-style diet loaded at 100ml per kilogram of body mass for three days, then cut fluids on the final day, and lost around two and a half per cent. The takeaway he gave Liam was blunt: “three days is all you need”.
Overdoing fluids is not harmless. Drinking excessive water can cause fluid overload, which Peter noted “could potentially” be fatal, the same mechanism seen in some marathon runners. This is exactly why water loading needs supervision, not guesswork.
6. Rehydration and the post-weigh-in refuel
Making weight is only half the job. The post-weigh-in window is where the fight is won or lost, and Peter treats it as seriously as the whole camp.
- Fluid first. Replace lost weight at roughly 1.5 litres of fluid per kilogram lost. Water alone is one of the worst rehydration choices because it dilutes electrolytes and gets passed straight out; if you need to urinate within half an hour, it has gone wrong. Use an electrolyte drink instead.
- Then fast carbohydrates. Aim for up to around 10 grams of carbohydrate per kilogram of body mass, using fast-digesting sources such as sports drinks, jellies and cereal rather than 700 grams of potato.
- Keep fat and fibre low. A big post-weigh-in pizza is high in fat and fibre, slows digestion and leaves you feeling awful. Lean meat with white rice does the job.
These principles line up with published acute-weight-loss and rehydration guidance for combat athletes (Reale et al., 2017; Barley et al., 2018).
7. How Condition Nutrition approaches a fight week
Condition Nutrition was built on real fight-week experience at world-title level. Peter has guided 20 world champions through full camps across MMA, boxing, Muay Thai and kickboxing. He is clear that there is no cookie-cutter plan: what works for one fighter fails for another, and the best results come from working together across multiple camps rather than parachuting in two weeks out. If you want expert eyes on your cut, these are the options:
- Elite Fight Camp Support — full-camp periodised nutrition from day one to fight night.
- Elite Fight Week Support — a precise plan and daily feedback for the hardest seven days.
- VIP Pro Support — year-round, end-to-end support for professional and title-level athletes.
Frequently asked questions
How do you cut weight for a fight without losing power?
Lose most of the weight gradually as fat across fight camp, aiming to be around 8% above fight weight one week out. In fight week, drop the rest by reducing carbohydrates, fibre and salt, with short water loading only if needed, then rehydrate and refuel properly after the weigh-in. Crash starvation and last-minute sauna cuts are what cost you power.
What should you do in fight week to make weight?
Use three levers rather than the sauna. Reduce carbohydrates to around 30 to 50 grams a day, cut fibre to under about 10 grams a day to clear gut residue, and cut salt to release water. Keep eating properly right up to fight week, because if you strip carbs out weeks early you have nothing left to manipulate safely.
How long should you water load before a fight?
About three days. A fight-week protocol of roughly 100ml of fluid per kilogram of body mass for three days, then cutting fluids on the final day, is enough to drop a couple of per cent. Drinking eight to fourteen litres a day for a week or more is unnecessary and can be dangerous, because excessive fluid intake risks fluid overload.
How should you rehydrate after a weigh-in?
Replace lost weight at roughly 1.5 litres of fluid per kilogram lost, using an electrolyte drink rather than plain water, then add fast-digesting carbohydrates up to around 10 grams per kilogram of body mass. Keep fat and fibre low to avoid slowing digestion. If you need to urinate within half an hour of drinking, you have rehydrated incorrectly.
References
- Reale R, Slater G, Burke LM. Acute-Weight-Loss Strategies for Combat Sports and Applications to Olympic Success. Int J Sports Physiol Perform. 2017;12(2):142–151. https://doi.org/10.1123/ijspp.2016-0211
- Barley OR, Chapman RF, Garvican-Lewis LA. The Current State of Weight-Cutting in Combat Sports. Front Physiol. 2018;9:1562. https://doi.org/10.3389/fphys.2018.01562
- Foo WL, et al. A Short-Term Low-Fiber Diet Reduces Body Mass in Healthy Young Men: Implications for Weight-Sensitive Sports. Int J Sport Nutr Exerc Metab. 2022;32(4):256–264. https://doi.org/10.1123/ijsnem.2021-0192
About the author
Peter Miller is a combat sports nutritionist and the founder of Condition Nutrition. He holds a Master’s degree in Sports and Exercise Science (University of Chester) and an ISSN Diploma in Sports Nutrition (Middlesex University), and is also a qualified chef. He has supported 20 world champions through full fight camps and is the sole author of this article.
