Men vs women: Nutrition

Dr Linia Patel explains the differences between men and women when it comes to nutritional needs.

You’ve heard it before: men are from Mars; women are from Venus. The popular relationship book tried to explain the reasons why men and women often appear to communicate, behave and express emotion differently. And now, the science also shows that men and women are different when it comes to nutrition.

The data gap¹

Medicine sees our reproductive organs and hormones as the greatest source of difference between men and women. Yet, despite fundamental physiological differences, for centuries we assumed (and sold the idea) that women and men work the same way and can be fixed the same way. The reality is we actually don’t have much science focusing on women. The fluctuation of multiple hormones and the different hormonal phases women go through is seen as a ‘challenge’ to a researcher. Consequently, a sex data gap exists. Take research in sport and exercise science as an example. Out of 5,261 studies from six sport and exercise science journals between 2014 and 2020, only 6% were carried out exclusively on females. Of the 1,211386 participants, only 33% were female. Of the 1,631 publications that included males only, 14% had a title illustrating this, whereas of the 328 publications that included females only, 63% had this in their title. Women are understudied, underdiagnosed and undertreated. Fortunately, in recent years there has been a big drive to improve the sex/gender gap in research – we know more now about how women work than ever before. However, there is still a long way to go.

What we know: the power of hormones

It’s no secret that women have menstrual cycles. During this cycle, the main female hormones oestrogen and progesterone go from low levels (luteal phase) to elevated levels (follicular phase) before dropping again; this drop is what causes a woman’s menstrual cycle^2,3. Other than menstruation, these reproductive hormones impact on many systems of the body, from fluid regulation to metabolism to maintaining core body temperature and how we sleep^2-4! At the menopause, there is a dramatic drop in all-female reproductive hormones and, post-menopause, these levels remain low⁶.

Men, on the other hand, don’t have the same peaks and troughs of hormones as women do, nor do they have the same hormones. Testosterone is the main sex hormone in men. Most testosterone is made in the testicles. Small amounts are also made in the adrenal gland (in the kidney)³. Testosterone plays an important role in libido, muscle mass, fat distribution, bone mass and the production of sperm. A small amount of circulating testosterone in men is converted into oestradiol, a form of oestrogen. As men age, they often make less testosterone and, consequently, oestrogen; however, this decrease is often gradual^3,5. Women have testosterone too; however, in much smaller levels than men⁴.

The female hormonal lifespan

Across the lifespan, women experience important hormonal milestones. All these stages alter how the female body functions. Of course, there are many variations to the norm and, as we age, this may change. The hormonal lifespan of a female is generally divided as follows^3,4,6:

1. Menarche. The first period and onset of puberty is where nutritional differences between males and females become apparent. During the menstrual cycle, women have different calorie and nutrient requirements due to fluctuations in sex hormones, namely progesterone and oestrogen. Not only do these hormones influence the monthly cycle but also body temperature, metabolism and food cravings.
2. Pregnancy (for some). When a woman is pregnant, she experiences a rampage of hormones that are essential to helping the foetus grow and prepare her for birth and breastfeeding.
3. Menopause. The menopause is when a woman has no menstrual period for 12 consecutive months. In the UK, the average age is 51 years, although this varies between ethnic groups. Post menopause refers to the period after menopause.

Changes that happen during a woman’s menstrual cycle³

Fluctuating hormones, while they may be considered a complexity for researchers, in reality provide additional insight into the inner workings of female bodies:

• During the first half of the menstrual cycle (follicular phase), a woman is in a low hormone phase, which is when, hormonally speaking, we are most ‘similar’ to men. Oestrogen is high, without progesterone, during the first half of the menstrual cycle. Research indicates that, in this phase, a woman is more anabolic (muscle building).
• During the second half of the menstrual cycle (luteal phase), hormones are high. Both oestrogen and progesterone are high, which means women’s bodies become more catabolic (muscle breakdown) and there is a need to ensure women have the right nutrition and recovery strategies in place.

Nutritional requirements: men vs women

Energy intake

Women have the same energy requirement as men; however, new research shows that many active women overwhelmingly miss that mark and don’t eat enough. From a total energy standpoint, the paper explains that professional male and female athletes need to consume 40-60 calories per kilogramme of fat-free mass to meet their energy needs. A new study found that 88% of women in the study fell short of eating enough and had low energy availability⁷. Although this study is on professional football players, this situation is not confined to sport. In my clinical practice, I see this every day. This is backed by research, which shows that 45% of female recreational exercisers fall into the sub-clinical classification of low energy availability⁸.

Low energy availability is when your body goes into an energy-saving mode due to not receiving enough calories to cover the calories being burned⁹. Studies show that a female body can go into ‘energy save’ mode after only four days of not meeting her essential calorie intake (resting metabolic rate). You can liken what happens in low energy availability in your body to your phone. When the energy save mode is activated on your phone, the screen light is dimmed, the background apps turn off and the device slows down. Essentially, the same happens with the body. Bodily functions that are not immediately life sustaining (such as menstruation and the ability to conceive) get downregulated and shut down until more energy becomes available to the body^9,10. The impact of the downregulation of hormones means you are more likely to have weaker bones, increasing your risk of stress fractures⁹. Although both women and men are susceptible to low energy availability, women have a lower tipping point^9,10.

Macronutrients

Protein^11,12

New research reveals that the female hormones oestrogen and progesterone have different effects on muscle protein synthesis to men. This sex difference originates from how we metabolise protein in the liver. Women oxidise less protein and leucine (the branch chain amino acid that ‘switches’ on protein synthesis) than men. Add to this the fluctuation of hormones during the menstrual cycle. During the high hormone phase in the menstrual cycle, the high oestrogen inhibits protein synthesis and the high progesterone enhances muscle breakdown. So, women need to be more attentive to how they recover post exercise than men, as they are at more risk of breaking down muscle. For both sexes, protein is key to muscle adaptations to exercise as well as immune function; however, women need to get in there quicker! Post exercise, women’s ‘window of opportunity’ to recover is 30-45 minutes, whereas men may have up to three hours. Research findings indicate muscle protein synthesis is enhanced in women post exercise with the ingestion of approximately 20-30g of protein.

Within my clinical practice, I see too many women skipping their post-workout snack because they’re trying to lose weight. This is the wrong way to go about it – especially as a woman. It’s easy to think that, if you delay food post workout, you will prolong your fat burning (since the body has nothing left to burn) and thereby you will lose weight more effectively. In fact, the opposite happens. You may end up gaining weight. By withholding recovery fuel, you put your body into a catabolic state that stalls your recovery, dims your metabolism and increases your fat storage because the body is afraid it’s in a state of famine.

Carbs^2,3,10,13

Active females within their reproductive years need carbs. Men do too, but research shows that women in particular need to include carbs for optimal performance. Given the low-carb-frenzy social media, this may come as a shock to many people who have been following a low carb diet or recommend one. Low carb, if done right, can work well for men and menopausal women. It doesn’t work well for women within their reproductive years.

The research shows women perform best in a fuelled state. That means eating carbohydrates. The reason is that it seems the thing that fundamentally drives the female physiology is the need to reproduce. When the female brain perceives she is not getting enough nutrition, especially carbohydrate, she has a marked reduction in the production of kisspeptin, a neuropeptide that is responsible for sex hormones and endocrine and reproductive function, which also plays a significant role in maintaining healthy glucose levels, appetite regulation and body composition. That’s why intermittent fasting may help men get lean but it makes it harder for women to budge their body composition. It elevates the stress hormone cortisol, which signals for the body to hold onto body fat and turn down the resting metabolic rate.

As with protein, there are fluctuations in the quantity of carbohydrates women eat across their menstrual cycle. During the high hormone phase, women have a greater capacity for fat burning and sparing glycogen, both in the liver and muscle. During this phase, research has found women should stay on top of their carbohydrate intake, particularly during exercise. During the low hormone phase, compared to her age- and fitness-matched male counterpart, a woman can afford to reduce her carbohydrate intake slightly. However, the key is never to go low carb.

Fat intake^2,14

Fats provide benefits for men and women. They serve as an energy source, regulate hormones and genes, maintain brain health and make food tastier! In general, recommendations for fat intake for men and women are similar. It is recommended that 30% of calories come from fat. The focus should be on including more ‘good fats’, called monounsaturated and polyunsaturated fats, and keeping your saturated fat intake in check. Eating too much saturated fat can increase your risk of heart disease. New research also shows that eating too many omega-6 fats, found in many processed foods, are even worse for men than for women. So, men need to be more attentive about intake of saturated and omega-6 fats.

Micronutrients^2,3,6,13

Women need fewer calories than men as they are generally smaller but, in many cases, they have higher vitamin and mineral needs than men. Iron and calcium are of particular importance for women.

Females are at an increased risk of iron-deficiency anaemia compared to men, due to the monthly blood loss associated with menstruation. The average premenopausal woman needs 18mg of iron per day, compared to 8mg for men.

Bone health is important for everyone through every life stage, but women are at an increased risk of osteoporosis particularly after the menopause, which also contributes to the risk of fractures and falls – both of which have a huge impact on other aspects of health, independence and quality of life. There are key nutrients that work together for strong and healthy bones – in particular, calcium, vitamin D, protein, magnesium, phosphorus and vitamin K. The recommended calcium intake is 700mg for men and women. During breastfeeding, the recommended intake of calcium is 1,250mg. Women past the menopause are at high risk of brittle bones due to their levels of oestrogen and, therefore, older women need to be on top of their calcium intake.

Nutrition tips for women during their reproductive years

1. Eat enough. When a woman’s brain perceives the body is not getting enough nutrition, especially carbohydrate, it goes into energy save mode.
2. Don’t train fasted. Training fasted increases cortisol, which promotes fat storage and can decrease the available building blocks needed for other hormones.
3. Eat enough carbs. Not only does eating carbs help us achieve our body composition, but also helps maintain a healthy immune and stress response to exercise.
4. Recover quick. Eat within the hour post exercise. Ensure you include 20-30g of protein in your post-exercise snack.
5. Start tracking. Women looking to lead a healthy lifestyle and optimise training and nutrition should track their periods and alter their training and nutrition according to hormonal phases. Apps like Flo, Clue or Spot-on can help women track their cycles.

Nutrition tips for men through their lifespan

1. Quality matters. With any eating pattern diet, quality is key.
2. Do your homework. Before dabbling in any eating pattern, be sure to do your homework and know why you are doing it. One size doesn’t fit all.
3. Watch your fat intake. Focus more on the ‘good’ plant-based fats. Eat less processed food.
4. Dabble with intermittent fasting (IF). Metabolically, IF is beneficial for men. Speak to a dietitian or a trusted health professional to help you find out which type of fasting would work best for you.
5. Know your health numbers. Know your weight, body composition, cholesterol numbers, blood pressure and blood sugar numbers as a minimum. Knowing and tracking these numbers can improve your health.

This previously featured in the Fitpro digital magazine.

References

1. 1. Cowley et al (2021) “Invisible Sportswomen”: The Sex Data Gap in Sport and Exercise Science Research, Women in Sport and Physical Activity Journal, 29(2): 1-6.
   2. Holtzman B & Ackerman K (2021), Recommendations and nutritional considerations for female athletes: Health and performance, Sports Medicine.
   3. Tarnopolsky MA (2003), Females and males: should nutritional recommendations be gender specific?
   4. Helm et al (2021), Impact of nutrition-based interventions on athletic performance during menstrual cycle phases: a review, Int Environ Res Public Health, 18(12): 6,294.
   5. Leblanc et al (2015), Differences between men and women in dietary intakes and metabolic profile in response to a 12-week nutritional intervention promoting the Mediterranean diet, Journal of Nutritional Science.
   6. Gould L et al (2022), Metabolic effects of menopause: a cross-sectional characterization of body composition and exercise metabolism, Menopause, 29(4): 377-89.
   7. Morehen J et al (2022), Energy expenditure of Female International Standard Soccer Players: A doubly Labelled Water Investigation, Med Sci Sports Exerc., 54(5): 769-79.
   8. Slater et al (2016), Female Recreational Exercisers at risk for low energy availability, J Sport Nut Exerc Metab., 26(5): 421-27.
   9. Ackerman et al (2019), Low energy availability surrogates correlate with health and performance consequences of Relative Energy Deficiency, Sport. Br J Sports Med, 53(10): 628-33.
   10. McKay et al (2022), Six days of Low carbohydrate, low energy availability alters the iron and immune response to exercise in elite athletes, Med Sci Sports Exercise, 54(3): 377-87.
   11. Roepstorff C, Steffensen CH, Madsen M et al (2002), Gender differences in substrate utilization during submaximal exercise in endurance-trained subjects, Am J Physiol Endocrinol Metab, 282(2): E435-47.
   12. Hausswirth C. and Le Murr Y (2011), Physiological and nutritional aspects of post-exercise recovery: Specific recommendations for female athletes, Sports Med., 41(10): 861-82.
   13. Tarnopolsky MA (2008), Sex differences in exercise metabolism and the role of 17-beta estradiol, Med Sci Sports Exerc., 40(4): 648-54.
   14. Bakija et al (2021), The impact of type of dietary protein, animal versus vegetable in modifying cardiometabolic risk factors: a position paper from International Lipid expert Panel (ILEP), Clinical Nutrition, 40: 255-76.