10 min read
3 Female Only Studies You Need to Know About
Guest author Chloe Salter
This International Women's Day we have a guest blog from Clinical Nutrition student and the creator of Female Performance Project, Chloe Salter. To shine some light on the power of the female body, Chloe has put together a round up of recent female only nutrition studies.
There are very limited studies involving nutrition, and even less sports-related nutrition, on women. There are a number of studies on obese and overweight women, and we often see the word ‘untrained’ when we look at the participants in female nutrition studies. There is a huge gap in studies where ‘fit’ women are concerned.
It’s understandable that there is more clinical research on those who are unhealthy or suffer from obesity - however, there is not the same gap in men’s research between studies on trained and untrained men. In an analysis of sports research, it was found that women only make up 35-37% of participants in studies in sports and exercise research.
I think it’s easy for us to sit and complain about the discrepancy between the representation of men and women in studies - but it’s also on us to volunteer for research, put ourselves forward, and educate ourselves so that we can be aware that there are substantial differences between sports nutrition for men and women. It is not one size fits all and we cannot assume that women will have the same results as men.
So here are 3 studies involving women that you need to know about:
Oral contraceptives and muscle growth
Molecular markers of skeletal muscle hypertrophy following 10 weeks of resistance training in oral contraceptive users and non-users, Oxfeldt et al, 2020.
This is a recent study that looked to see if oral contraceptives had any effect on strength and hypertrophy gains in female athletes. The participants were untrained, healthy women who had a regular menstrual cycle.
They were split into 2 groups, one group taking oral contraceptives and one without, and underwent 10 weeks of hypertrophy style bodybuilding resistance training.
Both groups made strength gains and experienced muscle growth, which would be expected going from no training to training on a regular basis - the famous newbie gains.
What is really interesting is that there were no differences between the rates of muscle growth between the two groups, and the oral contraceptive did not impede their gains.
Both groups saw a reduction in fat mass, although the greater overall loss of fat mass was in the non-contraceptive group.
The researchers also noted some evidence (very, very slight) which supported an androgenic effect due to the oral contraceptive - meaning that there could have been more anabolism occurring in the women who took the oral contraceptive. While there is not enough evidence to make any big claims, there is a hint of a suggestion therefore that oral contraceptives may even support muscle growth due to the androgenic effect of estrogen.
Oral contraceptives are not going to mess with your gains!
Keto diets in trained women
Effects of a ketogenic diet on body composition and strength in trained women, Vargas-Molina et al, 2020
Just like intermittent fasting, keto diets are currently very popular with claims that they are something of a magic fix. With intermittent fasting, we can see that there are benefits for men which involve increased growth hormone and anabolism - however as we found out before in the IF blog, as women we do not quite reap the same benefits!
I’ve seen claims across the internet and Instagram that like with IF, keto is a fast track to muscle growth. Is there actually any evidence for this?
A female-only study looked at 21 trained women (I was just excited to find any study which involved women who were active!) and followed them over 8 weeks while they undertook a strength program.
They were split into two groups, one which followed a keto diet, and one which continued to eat their regular diet.
Those not on keto saw minimal changes in fat free mass, but the keto group saw no changes (this means no increase in muscle tissue). Those on keto lost weight - due to being in a caloric deficit.
At the end of the 8 weeks, strength and power output was retested. While the keto group saw improvements in power output through a vertical jump test, there were no improvements in strength tests such as 1RM bench or squat.
The non-keto group saw improvements across all measures of power and strength.
This study shows us that keto may be a useful tool for weight loss, however, it does not lend itself well to performance in strength-based sports. It’s important to note that the keto group lost weight, and so this emphasises something that we already know and need to read over and over again - if performance is your priority, you should not be in a deficit!
Women may recover faster than men
The effects of recovery time on strength performance following a high-intensity bench press workout in females and males, Judge et al, 2010
This study looked at 6 males and 6 females who are listed as ‘athletes’ in college. They followed a 3 week resistance program which was oriented around improving pressing. At the end of the 3 weeks, they tested their 1RM bench press regularly at intervals over the following 3 weeks. In order to test recovery, the participants had to hit the same percentages of their 1RM again at time intervals, such as 4-48 hours post training.
The men in the study showed decreased strength at the 4 and 24 hour intervals following, whilst the women did not see any decrease in strength even after just 4 hours.
A supporting study in 1993 by Hakkinen demonstrates that faster recovery time in women may be down to a slower time to fatigue. In this study, muscular fatigue in the lower body was tested through 20 repeats of 1RM effort squats (ouch!). The maximal force output during exercise decreased faster in the male participants than the women, and then when testing at hour intervals following training, the women saw maximal force output recover substantially after an hour. The men took longer to recover, although ‘thereafter’ (the exact recovery time is not noted) the recovery was at a similar rate.
The fact that the women recovered quicker than the men in this study may be more down to the fact they were slower to fatigue in their squats and therefore needed less recovery time in comparison.
If we pair these studies up with the blog I recently wrote on intermittent fasting, it is blindingly obvious that there are huge differences between genders when it comes to recovery, fatigue, hormonal sensitivity to energy balance.
Nowadays there are websites and books on the shelves which promote certain diets and training programs for the general population - how many of these have included women in their research? Are they advertising to both genders having not taken into account variations where women are concerned?
One size does not fit all - and at the end of the day, there are not just gender differences, but genetic differences too! It’s important to be aware that performance and nutrition is highly individual and it’s down to us to note how we feel and perform based on what we are eating, how we are recovering, and more importantly for women, where we are in our menstrual cycle.
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