Written by Dr Zeeshan Afzal (MBBS) — Medical Doctor & Medical Content Lead, Welzo
Medically reviewed · Evidence-based · Aligned with UK clinical guidance
Last updated: July 2026 · Reading time: ~13 minutes
Everything attributed to Conor McGregor and his coaching team comes from published interviews with those coaches, or from documented reporting. Where a figure is widely repeated but unsourced, we say so rather than passing it on.
The genuinely interesting thing about Conor McGregor's preparation is not what he eats. It is the machinery around it — a nutritionist who logs every gram, a movement coach who was an outlier in the sport, and a weight-cutting process that is the single most dangerous routine practice in combat sport. That last part is what most articles skip.
Conor McGregor, born in Dublin in July 1988, is a mixed martial artist who became the UFC's first simultaneous two-division champion, holding the featherweight and lightweight titles. He trains at SBG Ireland under head coach John Kavanagh, who also awarded his Brazilian jiu-jitsu black belt.
He is 5ft 8in and has competed across three weight classes: featherweight (145 lb), lightweight (155 lb) and welterweight (170 lb). That 25 lb spread across the same body is the fact this article is really about.
Because it is unusually well documented through his coaches, who have given detailed interviews about the methods. And because his career includes both the best-resourced version of weight management in the sport and, earlier, some of its most punishing cuts.
Three names matter.
John Kavanagh — head coach at SBG Ireland, an engineering graduate with a famously analytical approach to the sport.
George Lockhart — a former US Marine and MMA fighter turned nutritionist, brought in by Kavanagh three weeks before McGregor's first fight with José Aldo. Lockhart takes complete control of a fighter's diet during camp, shopping and cooking several times a day and adjusting according to that day's training and weight. Lockhart has said the collaboration produced the easiest cut to 145 lb McGregor had had. Nutritionist Tristin Kennedy, who first worked under Lockhart, later took over full time.
Ido Portal — a movement specialist rather than a martial arts coach, whose involvement was considered unusual in MMA at the time and who influenced McGregor's mobility and locomotion work.
Kennedy told ESPN that he lays out everything McGregor consumes to the gram — macronutrients and individual micronutrients — adjusted daily against training load and metabolic rate, and he was candid that few other MMA athletes have that resource.
That candour matters. The precision people admire in elite fight camps is a function of a full-time professional, not of any dietary principle you can copy from an article.
Lockhart's stated principles are unglamorous: quality meat and fish, fresh vegetables, complex carbohydrates, and a strong emphasis on reducing added sugar. Simple carbohydrates are used deliberately rather than avoided — largely reserved for after training, when glycogen replacement is the priority.
Documented meals across camp reporting are exactly what that description implies: chicken, salmon, steak, sweet potato, rice, green vegetables, salad.
Lockhart's view is that most people do not need large amounts of carbohydrate — but a fighter training three times a day does, in order to keep glycogen stores available for explosive work. Timing them after training rather than before is a reasonable approach for someone with that training density.
For someone training three hours a week rather than three hours a day, the same reasoning does not apply. This is the most common error people make in copying athlete nutrition: adopting the carbohydrate strategy without the training load that justifies it.
You will see a figure of around 4,000 calories a day across nine meals attributed to his camp. We could not trace it to a first-party source, so treat it as reported. What his nutritionists have actually described is a daily-adjusted intake rather than a fixed number, which is a more sensible way to think about it anyway.
Most people misunderstand what fighters do. It is worth setting out clearly, because the misunderstanding is where the danger lives.
A fighter's weight cut has two distinct phases:
After the weigh-in, usually around 24 hours before the contest, the fighter rehydrates and refuels aggressively to regain the lost mass.
The first phase is nutrition. The second phase is not weight loss at all — it is controlled dehydration, and it is the part that causes harm.
The International Society of Sports Nutrition position stand on nutrition and weight cutting for combat sports sets out detailed post-weigh-in protocols: oral rehydration solutions at roughly 1 to 1.5 litres per hour with a sodium content of 50–90 mmol/L taking priority, followed by fast-acting carbohydrate at up to about 60 g per hour, with fibre limited to avoid gastrointestinal distress. Where significant glycogen depletion was used, post-weigh-in carbohydrate of 8–12 g per kilogram may be appropriate; for modest restriction, 4–7 g/kg.
The same document is explicit that the long-term health effects of repeated weight cuts are unknown.
This is the section that justifies the article.
In late 1997, three American collegiate wrestlers died within weeks of each other from hyperthermia and dehydration during rapid weight loss, having lost between 6.7% and 10% of body weight. The cases were reported in JAMA and led to significant rule changes in collegiate wrestling.
In December 2015, the 21-year-old flyweight MMA fighter Yang Jian Bing died following attempts to make weight. Other deaths, including those of younger athletes, have been reported since.
Fighters generally regain the weight, but that is not the same as rehydrating. One study found 39% of MMA fighters entered competition in a dehydrated state. Entering a combat sport contest dehydrated is associated with increased injury risk, and there is concern that reduced cerebrospinal fluid volume offers less cushioning to the brain.
Reviews suggest that moderate rapid weight loss — under about 5% of body mass — is unlikely to impair short-term performance. Beyond that, the risks of dehydration, electrolyte disturbance and renal dysfunction rise sharply. Elite fighters routinely go well beyond 5%.
Young athletes are at greater risk, not less. Under-18s have a less mature sweating response and regulate temperature differently, making them more prone to a dangerous rise in core temperature — particularly in saunas. Rapid weight loss should not be part of youth combat sport. If your child's coach is discussing a weight cut, that is a conversation to have with a doctor.
Camp training runs to roughly three to four hours daily across two sessions, separating skill work — striking, grappling, wrestling, cage work — from strength and conditioning.
The more distinctive element is the movement work. Bringing in a movement specialist rather than a conventional strength coach was unusual in MMA, and the emphasis on locomotion, mobility and unconventional patterns was ahead of where the sport generally was.
Not the volume. But the principle that mobility and varied movement deserve dedicated training time, rather than being a warm-up afterthought, is sound and applies at any level. It is also the element most likely to keep you training into your fifties.
McGregor's 2021 tibia and fibula fracture and the long rehabilitation that followed is a reminder of something the highlight reels omit: elite combat sport carries serious injury risk, and returning from a major fracture takes months of structured, supervised work rather than willpower.
McGregor's principal business ventures are an Irish whiskey brand and a stout. We are not going to pretend that has a place in a health routine.
UK guidance is to drink no more than 14 units a week, spread over three or more days, with several drink-free days. Current advice is that there is no completely safe level of drinking. Alcohol also directly impairs the things a training routine depends on: it disrupts sleep architecture, blunts muscle protein synthesis, and worsens rehydration.
An adult can weigh that up and make their own choice. It should just be made with accurate information.
Adequate protein. Morton and colleagues (2018) pooled 49 randomised trials and 1,863 participants, finding gains in strength and fat-free mass plateau around 1.6 g per kilogram of bodyweight daily.
Creatine monohydrate at 3–5 g daily, per the ISSN position stand — well suited to the repeated high-intensity efforts of combat sport.
Carbohydrate periodisation around training for athletes with genuinely high training loads.
Structured rehydration with sodium after significant fluid loss. Water alone is not adequate replacement.
Electrolyte supplementation during long or hot sessions. Magnesium for muscle function and sleep. Omega-3 and vitamin D, the latter recommended in the UK through autumn and winter.
Rapid weight loss by dehydration beyond modest levels, water loading, and sauna-based cutting without medical supervision. These are not grey areas.
Weight cutting is the single most dangerous practice in this entire article series. It is done by professionals with nutritionists, medical staff and commission oversight, and it still causes harm. It has no place in recreational training.
Head trauma, joint injury and fracture are inherent risks. If you take up MMA or boxing, do it at a properly coached gym with graduated sparring, and take head impacts seriously — suspected concussion means stopping, not continuing.
Analytical studies summarised in a 2023 review of supplement adulteration found that between 14% and 50% of sampled sports supplement products contained undeclared prohibited substances. If you compete under anti-doping rules, batch-tested certification is not optional.
What to look for on a label
A single named ingredient rather than a proprietary blend. The dose stated in the form that matters — elemental magnesium, not the weight of the compound. And third-party batch testing with a published certificate of analysis.
For fluid and electrolyte replacement around hard training, an electrolyte formula with meaningful sodium is the relevant category — sodium is what actually drives rehydration. Magnesium is a separate question: worth considering for muscle function and sleep rather than for fluid balance. Note that the L-threonate form below is chosen for sleep and cognitive purposes; for general magnesium repletion, a citrate or glycinate is usually the better fit.
Welzo Ultra Purity Magnesium L-Threonate 2000mg
2,000 mg magnesium L-threonate per three-capsule serving · taken 1–2 hours before bed · third-party tested with a published certificate of analysis · no proprietary blends
View product →For amateurs and recreational competitors, the sensible approach is to pick the class your walking-around weight fits, arrive hydrated, and fight there. You will perform better than a dehydrated version of yourself in a lower class.
If you genuinely need to change weight class, do it across months through a modest calorie deficit and adequate protein — not across days through water loss. That is the safe half of what fight camps do.
For sessions over about an hour, or in heat, replace sodium as well as fluid. Water alone can dilute blood sodium after heavy sweat losses.
Dedicated mobility work is the most transferable thing in his camp, and the thing most likely to keep you training for decades.
Protein to reach roughly 1.6 g/kg, creatine at 3–5 g daily, electrolytes for long sessions, vitamin D through the UK winter. Our minimal evidence-led stack guide covers the reasoning.
Quality meat and fish, fresh vegetables and complex carbohydrates, with simple carbohydrates used mainly after training. His nutritionist adjusts intake daily against training load rather than following a fixed plan, and logs macronutrients and micronutrients to the gram.
In two phases: gradual fat loss across the training camp, then acute dehydration in the final days through fluid restriction, sweating, saunas and hot baths. They rehydrate after the weigh-in. The second phase is not fat loss at all — it is controlled dehydration, and it is the dangerous part.
Yes, and it has been fatal. Three collegiate wrestlers died in late 1997 from hyperthermia and dehydration after losing 6.7–10% of body weight, and MMA fighter Yang Jian Bing died in 2015 while making weight. Risks include hyperthermia, dangerously low blood sodium, kidney injury and impaired cognition.
Drinking very large volumes of water in the days before cutting, to encourage fluid loss. It has been associated with hyponatraemia — dangerously low blood sodium, which can be fatal — and with kidney damage. Research suggests around 57% of UK MMA fighters use it. It should not be attempted without medical supervision.
Reviews suggest rapid losses under about 5% of body mass are unlikely to impair short-term performance. Beyond that, risks rise sharply. For amateurs, the safer approach is to compete at your natural weight rather than cut into a lower class.
No. Under-18s have a less mature sweating response and regulate temperature differently, making a dangerous rise in core body temperature more likely, especially in saunas. If a coach raises weight cutting for a young athlete, involve a doctor.
With sodium, not water alone. Position stand guidance for combat athletes prioritises oral rehydration solutions of roughly 1–1.5 litres per hour containing 50–90 mmol/L sodium, followed by fast-acting carbohydrate. Water alone can dilute blood sodium after large losses.
If they are training three times a day, yes — glycogen availability limits explosive work. That reasoning does not transfer to someone training a few hours a week. Copying an athlete's carbohydrate strategy without their training load is the most common mistake here.
Yes. It disrupts sleep architecture, blunts muscle protein synthesis and worsens rehydration. UK guidance is no more than 14 units a week spread over three or more days, and current advice is that there is no completely safe level.
The dedicated mobility and movement work, the structure of separating skill sessions from conditioning, adequate protein, and gradual rather than acute weight management. Not the dehydration.
Medical disclaimer. This article is for general information and is not medical advice. Conor McGregor has no connection to Welzo and does not endorse Welzo or any product mentioned. Nothing here is a guide to rapid weight loss or weight cutting, and nothing should be taken as a claim that any supplement prevents, treats or cures disease.
Rapid weight loss by dehydration carries a risk of serious harm and death. It should only ever be undertaken by professional athletes under medical and specialist supervision, and never by anyone under 18.
Speak to your GP before starting combat sports training if you have a heart condition, kidney disease or high blood pressure. If your relationship with food or your weight is causing you distress, support is available — in the UK you can contact the National Alliance for Eating Disorders, or speak to your GP.
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