Why McGregor Looked 20 lbs. Heavier than Mayweather

Photo from: New York Post

Given the recent Mayweather/McGregor fight, a fight with a clear size difference between fighters, I thought I’d explain the art and science of weight-cutting, and how this phenomenon relates to nutrition, health, and performance.
 
If you didn’t see the fight or weigh-in, a few key facts include:

• The weight class was 154lbs
• Mayweather weighed-in at 149.5lbs
• McGregor weighed-in at 153lbs
• McGregor looked slightly larger than Mayweather at the Weigh-In
• McGregor looked massively larger than Mayweather in the Fight

 
The fact that McGregor was TKO’d in the 10th round is actually of remarkably little importance here. I’m not usually one to say that winning and losing is not important; it is clearly a performance indicator. But in this case, I really don’t think you can measure his performance on a binary scale given all the other variables (i.e. their existing skill sets and experience in boxing). What I would like to focus on more is that McGregor had what appeared to be a slight size advantage at weigh-ins, become quite a large size advantage on the night of the fight. So how did McGregor put on what looked like 10-20 lbs. of lean mass in 24 hours?
 
Now, I’m speculating here that McGregor followed this standard weight-cutting process I’m about to describe. He was the larger athlete and had a what looked like a drastic increase in size from Weigh-Ins to Fight, but keep in mind that I don’t actually work with him, and don’t actually know what he weighed leading into weigh-ins or on the night of the fight. However, I know this process intimately. I’ve work with athletes on weight management, but more importantly I have personally cut-weight more times than I can count. Near the end of my wrestling career, my weight would bounce from 65kg (143lbs) at weigh-ins, to about 73kg (161lbs) in competition the next morning.
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Weight-Cutting 101:

• How Weight-Class Competitions Work – Any sport that has weight-classes also has weigh-ins (or multiple weigh-ins). An athlete must weigh equal-to or less-than their weight-class at weigh-Ins in order to compete. However, what they weigh in competition is unimportant (in terms of qualifying to compete, it could have importance for performance).
• What Is The Point In Cutting-Weight? – The point is to qualify for competition by making a weight-class, but weigh more at the time of competition (presumably because there is an advantage to weighing more).
• What Are The Possible Advantages? – It is very important to understand that these advantages occur at the time of competition and not at the time of weigh-ins. Advantages usually come from the relative increase in muscle mass that go along with being heavier. That is, if body composition (i.e. body fat %) has not already been optimized, “cutting-weight” will not likely improve performance.
• What Is Actually Happening In A Weight-Cut? – Cutting-weight is strictly the fluctuation of fluids. Fluids are the only way that body-weight can change this drastically in such a short amount of time. Therefore, it is essentially controlled and purposeful dehydration. This is not to say it isn’t dangerous, but it is purposeful. Upon weighing-in, the athlete must attempt to regain those fluids in order to rehydrate. Remember, no actual competing is occurring while the athlete is dehydrated. If the athlete cannot regain the fluids adequately, then they may be competing in a dehydrated state, which is bad for both performance (muscle weakness, decreased aerobic capacity, decreased glycogen storage, electrolyte imbalance, etc.) and health (cardiovascular health, renal health, concussion risk, etc.).
• What It Is Not – Cutting weight is not the decrease in body fat %, or the increase in lean muscle tissue. It only has an impact on aesthetics due to dehydration (which can’t be maintained for a significant amount of time). Again, body composition should be optimized (see how lean McGregor is), before even considering any of the advantages of cutting-weight.
• How Is It Done? – There are a few tricks, but an athlete should always work up to larger weight-cuts, as every athlete reacts differently, and has different capacities to lose fluids and/or function while dehydrated. Remember, these all revolves around losing fluids in a relatively short period of time:
  • Stop drinking fluids – The longer this happens, the more fluids that aren’t in the system. To give this some perspective, if you were to drink a 500ml bottle of water, you will weigh 1lb more. Keep in mind that dehydration can impact performance and health in the training leading up to weigh-ins as well, which is not favourable. If you stop drinking fluids too early, your preparation for competition may suffer.
  • Decrease sodium intake – Sodium retains water, and by decreasing the sodium in a diet in the days prior to weigh-ins, fluids will be lost quicker.
  • Decrease carbohydrate intake – Decreasing carbohydrate intake leads to decreases in glycogen/energy stores (which hold water). Although effective, this method impacts performance in training prior to weigh-ins two-fold: decreases in fluids and decreases in energy stores.
  • Sweat more – Sweating is really the only way to directly control the elimination of fluids from the body. Increasing body temperature via additional clothing, exercise effort, environmental temperature (e.g. sauna, hot tub) will all lead to increases in fluid loss via sweat.
• How Much Weight Can Be Lost? – Assuming body composition is stable and optimized, then the amount of weight (or dehydration) that can be lost should actually be dictated by the time frame between weigh-ins and competition. The longer the window, the more weight that can safely be put back on. Remember, even if an athlete dehydrates in a relatively safe manor, that athlete should not compete in a dehydrated state (or this is just as unsafe). So, athletes in competitions with morning/day-of  weigh-ins should utilize minimal amounts of “weight-cutting” (e.g. 2-3lbs).  While athletes with a 24 hour window (such as McGregor), can start working up >5% dehydration (e.g. >10lbs). 

**One key factor in regaining the weight is to replace what was lost. This not only applies to the fluids, but also the sodium and carbohydrate. Just as decreasing intake of sodium and carbohydrate decreases fluid retention, increasing intake will aid in fluid retention.
 
It is important to remember that I am not condoning “cutting-weight”, but merely explaining the phenomenon in hopes that a more knowledgeable athlete can make smarter choices. “Cutting-weight” can be very dangerous, and should be done so in a supervised manor, if done at all. Involve coaches in the decision, and speak with a dietitian about it. Think about the potential advantages, and how they weigh against the possible disadvantages and safety concerns of this practice before making any decisions.

Writer: Kevin Iwasa-Madge, Sports Dietitian, CSCS