Dear Dr Adam,
As a woman who likes to keep up with new studies in the world of exercise and sports nutrition, I’ve found that a lot of what I read online is heavily – if not exclusively – conducted on men. How reliable and useful are the discoveries from these studies for me?
This is an interesting one for a number of reasons, but first, let me explain why this tends to be the case. Sport – both professionally and academically – remains male-dominated. Study-wise, that means the likelihood of test subjects who come forward being men is far higher.
There is another reason, though, and that is that men are simpler. This doesn’t apply only to exercise studies, but what you find a lot of the time is that men are chosen in complicated intervention studies because women have a potential variability in terms of the menstrual cycle. If you were going to do an intervention in women, you might have to correct for that and repeat it every 28 days, as opposed to carrying it out over a 5-day washout – so a lot of it comes down to men just being more available.
As for whether the findings you’re reading are relevant to you, well obviously to some extent, men and women are not the same physiologically. In terms of protein intake, if you’re looking at it as gram per kg per day, that takes gender into account as women are typically of a lower weight than men, unless looking at the extreme end of the spectrum such as a female powerlifter. There is, however, nothing to suggest that you deal with that protein any differently, specifically at a dose relative to yourself.
That said, when you think of men and women of the same size, generally speaking, they’ll be different in terms of body composition. Men have less body fat and more lean mass compared to women of the same size (a typical body fat range for a man will be somewhere between 10 and 25%, and for a woman, 20 to 35%). There are simple design reasons for that – women needing that extra energy reserve for pregnancy lactation being one. There are also differences like where that fat is distributed and stored – women tending to store it in the buttocks and thighs compared to more centrally in men.
“If energy requirements are slightly different, then absolute macronutrients will also be different for a woman – the number of carbohydrates, proteins and fats they’ll need”
All of which links into some differences in how we metabolise things. Women tend to have a lower metabolic rate than a man of the same size as they have less fat-free mass, but they don’t have any less active muscle mass or any more or less active adipose tissue mass. That means men have a higher energy requirement for two reasons; one being that the man will be at a higher weight and the other that they’re going to have more lean tissue, which has a higher metabolic cost per unit of mass than women. From this comes inherent differences elsewhere – if energy requirements are slightly different, then absolute macronutrients will also be different for a woman – the number of carbohydrates, proteins and fats they’ll need.
We know now that actually, in terms of exercise, how men and women respond is slightly different. Men burn carbohydrates much more readily than women at a given intensity of exercise and are geared up to utilize this macronutrient more in their muscle. They also have less body fat and less circulating fat around the blood, so are less in tune with oxidizing fat for exercise as women are.
Not to say that women are burning pure fat, but at a given intensity they’d probably burn more than men. One of the interesting things we’ve looked at is how this gender difference isn’t so much to do with protein but carbohydrates, which in women could often be overdosed on in terms of performance around exercise compared to men.
Traditional performance nutrition advice reads that we should feed carbs before exercise, during (if it’s long enough), and replace afterwards. Perhaps that fairly aggressive strategy isn’t totally appropriate for women as they’re more able to oxidize fat instead as a supplementary fuel. The fact that there tends to be less of a woman also means they could be over-fueling altogether, irrespective of the fuel.
And so there are some study areas to approach with a degree of caution should findings be based solely or heavily on male participants. For the most part, though, this will simply be an exercise of scaling what you read to work for your body composition.
To have your nutrition questions answered by Dr Adam Collins, please email firstname.lastname@example.org