4 life-changing lessons from the world's best studies on exercise for women, by a female physiologist
For centuries, medical researchers have exclusively studied men. Despite the fact that women are physiologically very different, sex differences have been ignored, and findings have been carelessly extrapolated to women. This long-standing lack of female-based research is what exercise physiologist and nutrition scientist Dr Stacy Sims has devoted her career to: determining how women should exercise and eat for optimal health.
Speaking on The Diary of a CEO podcast last month, she said: ‘When we think about everything that we know for protocols from training to eating and recovery, it's based on male data. I'm looking at what I do and trying to empower women to understand their own bodies and maximise their potential.’
Though she acknowledges that there’s ‘still a lot of research to be done’, her efforts to decipher the findings of existing studies – and lead new ones – have been revolutionary. Here are her top insights from the best studies on exercise and nutrition for women, that she wants you all to know.
1. Women will see benefits from strength training faster than men
Research shows that resistance training is just as, if not more effective than aerobic exercise at reducing the risk of chronic diseases like type 2 diabetes, cardiovascular disease, and cancer.
One study of more than 12,500 people (both male and female) published in Medicine & Science in Sports and Exercise found that those who did any amount of strength training on a weekly basis had a 40-70% reduced risk of developing heart attack, stroke, or death related to heart disease compared with individuals who did no strength training, no matter how much aerobic exercise they did.
What’s more, other research demonstrated that women respond better to strength training than men. One study published in the Journal of Strength and Conditioning Research followed a group of female recreational athletes over the course of a 12-week periodised resistance training programme and found that they increased their strength by 30% at the end of the study, compared to 25% for men. The key is consistency, says Dr Sims.
2. Resistance training is the most effective method for women to burn fat – particularly abdominal fat
‘Contrary to the dogma that cardio burns fat and strength training builds muscle, resistance training is superior for burning fat in women – especially belly fat. One study published in the Journal of Applied Physiology was carried out on a group of young, healthy trained females and found that resistance training significantly increased the rate of fat burning on your belly,’ Dr Sims explains. How? The fact that resistance training builds muscle tissue – which is more metabolically active than fat – contributed, but the authors noted that the results were largely due to the hormones released when women lift weights.
The researchers inserted probes into the women’s subcutaneous abdominal fat to measure the level of stored fat breakdown (known as lipolysis) during exercise. These women then performed one set of 10 reps of a series of barbell exercises that included (in this order) a back squat, bench press, Romanian deadlift, bent-over row, shoulder press, and reverse lunges, and the same workout again, but this time with three sets of 10 reps. Both training sessions were performed in the early afternoon, and during menstruation (days one to six of the follicular phase).
This is particularly significant to note, Dr Sims says, as the menstrual cycle isn’t often taken into account by exercise researchers. The authors also intentionally avoided the high-estrogen mid-luteal phase, which can enhance exercise-induced fat burning in women.
‘During both sessions, the researchers found a significant increase in fat metabolism in the women’s abdominal area during and immediately after training, as well as increased whole-body fat burning and an increase in resting energy expenditure (how many calories you burn at rest) post-exercise, all of which were triggered by increases in the release of your growth hormone, epinephrine, and norepinephrine, which support fat metabolism,’ says Dr Sims.
3. Post-workout fuel matters more for women than men
Low energy availability (LEA) is extremely common in women. A 2019 survey of 1,000 female athletes across more than 40 sports published in the British Journal of Sports Medicine estimated the risk of low energy availability in women athletes at more than 47%. In other words, nearly half of active women aren’t eating enough for their body to perform basic functions like making muscle, regulating metabolism and maintaining homeostasis (the state of balance needed for all your body systems to survive and function correctly).
‘Undereating puts your body in a catabolic state that delays recovery, slows metabolism and increases fat storage because your body is afraid it’s starving, so it grabs onto the fat it currently has,’ says Dr Sims. Post-workout fuel is an important part of eating enough, and particularly as a woman. ‘During this “golden recovery window”, you’re not only primed to transport the carbs you eat straight into your muscle stores, but also to shuttle amino acids into your muscles, where they can repair the damage and build you back stronger.
‘It’s important to note that as a woman, your recovery window to take advantage of all these benefits is short – about 30 to 45 minutes (men may have up to three hours). After that point, your insulin sensitivity declines, so it takes your muscles longer to absorb the glucose from your bloodstream, and as a result, your overall glycogen storage is lower.’
Dr Sims refers to research in the journal, Medicine in Sports and Exercise Science, which shows that protein should be prioritised in every post-workout meal or snack. The study shows that women need protein after a workout more than men, because the sex hormone progesterone exacerbates muscle breakdown. Dr Sims recommends consuming 25-30g of protein within 30 minutes of a hard workout, in order to protect your muscles and help them to grow back stronger after training.
4. Exercising while pregnant is good for both you and your baby
If you’re worried that exercising while pregnant could harm the safety of either you or your baby, know that a 2019 meta-analysis including more than 32,000 women found that vigorous exercise into the third trimester of pregnancy didn’t adversely affect the outcome of birth, while vigorous exercisers also had a lower risk of premature birth. Other research in the British Journal of Sports Medicine, Dr Sims points out, shows that even women who have been inactive prior to pregnancy should gradually add exercise into their routine for their own health and for the health of their babies.
‘Training also improves the health of the placenta itself by improving its vascular function so the developing baby gets more blood flow, according to 2014 research published in Frontiers in Pharmacology,’ says Dr Sims.
‘Exercise is also good for your growing baby’s lungs, according to a new study presented in October at the European Respiratory Society International Congress, which showed that a pregnant mother’s physical activity is linked to the lung function in her offspring after birth.
‘The best advice I gave my students (as I was teaching training principles and practice, including pregnancy and exercise) was that the body is inherently smart. It does not allow you to go anaerobic when you are pregnant, and when you play it smart by listening to your body, you can have a very active, healthy pregnancy; good for the mother’s body and mind, and excellent for fetal growth, development, and future health outcomes.’
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