Effect of weight loss by ketogenic diet on body composition

An interesting study which is said to show good results for the keto diet and athletic performance (Hyun-seung Rhyu1 and Su-Youn Cho. The effect of weight loss by ketogenic diet on the body composition, performance-related physical fitness factors and cytokines of Taekwondo athletes . J Exerc Rehabil. 2014 Oct; 10(5): 326–331.).

The participants were randomly assigned to 2 groups, 10 participants to each group: the ketogenic diet (KD) group, and the non-ketogenic diet (NKD) group.

The diet/training period was only 3 weeks. The performances were compared:

Aerobic capacity was evaluated by measuring the time taken to finish a 2,000 m sprint. Whereas anaerobic capacity was evaluated by the Wingate test (), by measuring peak power, mean power and fatigue index using a Monark cycle ergometer (Monark 894-E, Sweden). Muscle strength was evaluated based on the measurement of: (1) grip force (TKK 5401, Takei, Japan) and back muscle strength (TKK 5402, Takei, Japan) using a digital measuring instrument, (2) muscle endurance by measuring the number of sit-ups performed in 60 sec, (3) instantaneous reactionary force by measuring time and distance on 100 m sprint and standing broad jump, respectively, and (4) balance by measuring duration on single leg standing with eyes closed.

The diet was only three weeks long. The body composition results were not great for Low Carb.

Changes in body composition

Variables KD (n= 10) NKD (n= 10) F-value


Pre Post Pre Post
Weight (kg) 64.11± 7.19 60.34± 6.59 63.69± 7.64 61.16 ± 7.84 G 0.004
T 89.927*
G×T 3.484
%Body fat (%) 12.59± 3.96 12.21± 3.59 11.31± 2.77 10.23 ± 2.63 G 1.283
T 4.486*
G×T 1.122
Lean body mass (kg) 54.65± 3.93 52.47± 4.67 54.94± 6.50 53.55 ± 8.16 G 0.067
T 10.457*
G×T 0.520
BMI (kg/m2) 21.44± 2.10 20.18± 1.79 21.08± 1.94 20.23 ± 1.97 G 0.032
T 86.936*
G×T 3.282

The KD kids lost twice as much weight which is good. The %Body fat wasn’t changed nearly as much in the KD group as in the NKD group. Worse than that, the KD group lost much more Lean Body Mass. BMI tracked the weight loss again demonstrating the weakness of the BMI measurement for tracking body composition. I think it may be the case that the LBM mass was mostly from lost water weight.

But how about performance?

  • KD did better on the 2,000 meter sprint after training than before. The NKD didn’t show much of an improvement. However, the timeframe listed in the results was 500 minutes. I don’t know how to make sense of that timeframe. It took the participants over 8 hours to sprint for a mile and a quarter?  Could the units be in seconds? If it was seconds then the time would be 8 minutes to run a little over a mile. That is possible in high school athletes.
  • What is striking is how much worse both of the groups did after training. Both groups lost peak power and mean power and the KD group lost significantly more power than the NKD group.
  • Another striking parameter was how much worse the NKD group got in anaerobic fatigue after the training. That is surprising.
  • The KD group did worse on grip strength gains.
  • The KD group did not improve as much on back muscle strength gains.
  • Both groups took longer on the 100m sprint.
  • Both groups could not jump as far in the broadjumps after training.
  • Equally disturbing was the lack of improvement in the sit-ups on the NKD group compared with the KD group.

All in all this points to a fatigued group for the final tests. It is possible to speculate that the KD group was less fatigued because the performed at a lower rate during the week or two of keto adaptation and stored up strength during that period. They show less signs of fatigue.

Issues with the study

  • One of the issues is that the performance tests were performed after fasting for 12-hours. That seems like a unlikely scenario which greatly benefits the Lower Carb cohort. In a more likely scenario both groups would have followed their diet.
  • There seems to have been no test such as RER or even measurements of urine ketones to verify ketosis in the Low Carb cohort.
  • The High School students were given lists of foods to eat. There were no food logs and no verification of compliance. There was no dietary analysis at all.
  • Muscle endurance was done by seeing how many situps could be done in 60 seconds.
  • There was no control group in diet.
  • The standard deviation bars on the data were much bigger than the change effects.

Taekwondo is characterized as:

a comprehensive physical exercise involving high intensity movement of the muscles and joints of the whole body at the mean 85–95% HR-max

Yet, I can’t find an explanation of the time duration of Taekwondo.

 

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.