• Mark Turnbull

The risks of rapid weight loss

Updated: Apr 10


Without doubt rider weight plays an important part in cycling, over the years the body mass of both male and female pro cyclists is getting lower and lower. The pressure to reach certain weights to gain a competitive advantage over opponents is reaching new extremes. As key races approach, riders reduce their body fat levels to extremely low levels.


This practice is carried out by world tour teams with the supervision of leading sports scientists and nutritionists, who are no doubt aware of the fine line they tread between what is actually safe and the pinnacle of human performance. It's not just a practice reserved for cycling, drastic weight making strategies are resulting in athlete deaths as recent as June last year (see HERE). With this in mind, the weight-making research group at Liverpool John Moores University aimed to describe the strategies of an individual male athlete as he made weight before competition and quantify the physiological and metabolic impact of the extreme weight cut.


What They Did The athlete presented was a 22-year-old professional male MMA fighter, with the contest under investigation for the case study being the defence of his featherweight championship. At the beginning of the camp he weighed 80.2 kg and was required to make weight at 65.7 kg over an 8-week period. They assessed the athlete at regular periods before and after the contest for body composition using DXA and skinfolds, resting metabolic rate, and peak oxygen uptake with blood samples taken and analysed at a local hospital.


The protocol of the 8-week weight-making period included the following phases:

1) 7-week energy restriction period.

2) 6-day water loading period.

3) An acute weight cut strategy.

4) Rehydration and refuel strategy

5) Ad libitum recovery period following the fight.


What They Found During phase 1, the athlete lost 4.4kg. During the “cut”, the athlete exhibited clear symptoms of the relative energy deficiency in sport syndrome, reductions in resting metabolic rate, the inability to complete the maximal oxygen uptake test and perturbations to endocrine status and hypercholesterolemia (high cholesterol).


In phase 3 during the cut to make-weight (weight-loss of 7.3 kg), the athlete experienced a significant stress response:

⇒ 3-fold increase in plasma cortisol

⇒ Evaluations in serum proteins

⇒ Elevations in plasma osmolality

⇒ Elevations in plasma sodium concentrations

The plasma sodium observed (148 mmol.L-1) was near to severe levels of hypernatremia (>150 mmol.L-1) where mortality may occur. Similarly, the relative and absolute changes in serum creatinine levels during the final phase of the weight cut are consistent with acute kidney injury.


Finally, following the 32-h rehydration and refuelling strategy, the athlete gained 10.6 kg in absolute mass and 2 weeks after the competition, resting metabolic rate, markers of endocrine status, lipid profile, hydrations status and kidney function had all returned towards normative ranges.


Practical Takeaways For practitioners and coaches working with athletes that are required to make-weight for competition, this case-study provides clear data showing the potentially harming effects of making weight poorly (specific to this individual).


The athlete showed clear signs of relative energy deficiency, evidenced by:

⇒ Reduced metabolic rate.

⇒ Inability to complete performance tests.

⇒ Alterations to endocrine hormones.

⇒ High cholesterol.

⇒ Dehydration induced hypernatremia.

⇒ Acute kidney injury.


Although based on one individual, this case study shows the harmful (and potentially fatal) effects of extreme weight cutting in MMA athletes and represents a call for action to governing bodies to safeguard the welfare of MMA athletes. Similar habits of making weight are being reported other sports elsewhere.


For me, the data presented from this research group is disturbing, and reveals how close the athlete was to potentially fatal outcomes, especially the acute kidney damage. Although this is an extreme example, it worries me that the image regular cyclists have of the best in the sport is just not a realistic target. Weight comes off with regular training and improved eating habits. Starvation and dehydration are not the way to go. So fuel your rides, don't be a slave to the scales and listen to your body. However, if you would like to loose some weight safely, athletes and coaches should seek help and advice from qualified dietitians and sport nutritionists before attempting to make weight.


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