Nutrition – Part 3 - Protein: The Building Block Your Body Can't Do Without

Protein seems to be the most talked-about macronutrient in the fitness world. So it's time to look at what science is telling us – specifically related to women who are active.

What is protein and why does it matter?

Protein is one of the three macronutrients your body needs (along with carbohydrates and fat). Unlike carbs and fats, which your body primarily uses for energy, protein serves as the building blocks for nearly everything in your body—your muscles, bones, skin, hair, hormones, enzymes, and immune system all depend on adequate protein.

When you eat protein, your body breaks it down into amino acids, which it then uses to repair and build tissues, make hormones and enzymes, and support countless other functions that keep you healthy.

Your body doesn't store protein the way it stores carbohydrates or fat, which means you need to consume adequate protein regularly to meet your body's ongoing needs.

Protein to build muscles

How much protein do you need?

The current Recommended Dietary Allowance (RDA) for protein is about 0.8 grams per kilogram of body weight. This guideline was established in 2005 by the Institute of Medicine (now the National Academy of Medicine) and represents the minimum intake needed to prevent deficiency rather than an optimal intake. This amount might be sufficient if you're completely sedentary, but it's nowhere near adequate for active women.

Research by Dr. Stacy Sims, an internationally recognised exercise physiologist specialising in women's health and performance, suggests that active women need significantly more protein than the standard recommendations.

For active women, Dr. Stacy Sims recommends 1.7-2.4 grams of protein per kilogram of body weight per day. This range allows for flexibility—aim for the lower end on easier days and the higher end on heavy training days.

What does this look like in practice? For a woman weighing 70kg (about 11 stone), this translates to roughly 120-170 grams of protein per day. If you're perimenopausal or postmenopausal, your protein needs can be higher.

Research suggests aiming for 40-45% of daily calories from carbohydrates and about 30-35% from protein, with the remainder from healthy fats.

Why do women need more protein?

Protein supports muscle maintenance and growth, especially important when you exercise. When you strength train, you create microscopic tears in your muscle fibres (a good thing). Protein provides the amino acids needed to repair these tears and build stronger muscle tissue.

As oestrogen levels decline during perimenopause and menopause, women develop "anabolic resistance"—your muscles become less responsive to the muscle-building effects of protein. To compensate, you need to consume more protein.

Adequate protein intake is essential for maintaining bone density and supports body composition. Protein helps you feel fuller for longer, supports metabolism, and when combined with strength training, helps maintain lean muscle mass while supporting fat loss if that's your goal.

Protein needs are also higher during the luteal phase of your menstrual cycle (the two weeks before your period). During this phase, progesterone is actually catabolic—it breaks down lean muscle mass. Consuming at least 30 grams of protein per meal during this phase helps counteract this effect.

Protein timing matters too

It's not just about the total amount—when you eat protein throughout the day matters for optimal muscle protein synthesis. Aim to distribute your protein evenly across meals, consuming protein every 3-4 hours. This helps maintain steady amino acid availability for your muscles and other tissues.

After exercise, try to consume 30-35 grams of high-quality protein within 45 minutes. For women in their reproductive years, 35 grams is the target.

Starting your day with at least 30 grams of protein at breakfast helps set the tone for stable blood sugar, reduced cravings, and better body composition outcomes.

Not all protein needs to be animal based

One of the biggest misconceptions about protein is that you need to eat meat at every meal to meet your needs. While animal proteins are complete proteins (containing all nine essential amino acids your body can't make on its own), you can absolutely meet your protein needs through plant-based sources—you just need to be a bit more intentional about variety and quantity.

Excellent plant-based protein sources include legumes and pulses (lentils, chickpeas, beans), soy products like tofu, tempeh and edamame, quinoa (one of the few plant-based complete proteins), nuts and seeds, and even vegetables like broccoli and spinach. The image I've included shows the protein content of various plant-based foods, and you might be surprised at how much protein these foods contain.

While most plant proteins are "incomplete" (meaning they don't contain all essential amino acids in optimal ratios), you can easily obtain all the amino acids you need by eating a variety of plant-based protein sources throughout the day. You don't need to combine them in the same meal—your body maintains a pool of amino acids that it draws from as needed.

plant based sources of protein

Start small

Just as we discussed with the previous nutrition posts, you don't need to overhaul everything overnight. Here are two simple changes you can start with:

Boost your breakfast. Most people eat very little protein at breakfast. Start your day with 30 grams—this could be three eggs with vegetables, Greek yoghurt with nuts and berries, a smoothie with nut butter, scrambled tofu with spinach and mushrooms, or a bowl of porridge made with soy milk topped with hemp seeds and almond butter. Notice how differently you feel throughout the morning when you start with adequate protein.

Audit your current intake. For just three days, track roughly how much protein you're eating at each meal. You might be surprised to find you're eating plenty at dinner but very little at breakfast and lunch. Once you know where the gaps are, you can address them strategically.

When choosing your protein sources, quality matters. Choose minimally processed options like whole beans, lentils, and tofu rather than heavily processed meat alternatives. Avoid relying heavily on processed meats like sausages, bacon, and deli meats, which are associated with increased health risks.

Different types of protein

The bottom line

Protein isn't just for bodybuilders or people trying to "bulk up." It's an essential nutrient that supports your muscles, bones, hormones, immune system, and overall health. For active women, adequate protein intake is particularly crucial—and most women simply aren't eating enough.

The good news is that whether you prefer animal proteins, plant-based sources, or a combination of both, you can meet your body's needs with proper planning. Focus on including protein at every meal, aim for the research-backed quantities that support your activity level and life stage, and pay attention to timing, especially around your workouts.

If you'd like to have a chat about nutrition to support your fitness goals, get in touch via the website and we can discuss your goals and create a path forward that works for your lifestyle.

References

Burd, N.A., Tang, J.E., Moore, D.R. & Phillips, S.M. (2009) 'Exercise training and protein metabolism: influences of contraction, protein intake, and sex-based differences', Journal of Applied Physiology, 106(5), pp. 1692-1701. https://doi.org/10.1152/japplphysiol.91351.2008

Institute of Medicine (2005) Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. Washington, DC: The National Academies Press. https://doi.org/10.17226/10490

Moore, D.R., Churchward-Venne, T.A., Witard, O., Breen, L., Burd, N.A., Tipton, K.D. & Phillips, S.M. (2015) 'Protein ingestion to stimulate myofibrillar protein synthesis requires greater relative protein intakes in healthy older versus younger men', The Journals of Gerontology Series A: Biological Sciences and Medical Sciences, 70(1), pp. 57-62. https://doi.org/10.1093/gerona/glu103

Pagliai, G., Dinu, M., Madarena, M.P., Bonaccio, M., Iacoviello, L. & Sofi, F. (2021) 'Consumption of ultra-processed foods and health status: a systematic review and meta-analysis', British Journal of Nutrition, 125(3), pp. 308-318. https://doi.org/10.1017/S0007114520002688

Sims, S.T. (2024) 'How Much Protein Is Enough?', Dr Stacy Sims Newsletter, 9 April. Available at: https://www.drstacysims.com

Sims, S.T. & Huberman, A. (2024) 'Dr. Stacy Sims: Female-Specific Exercise & Nutrition for Health, Performance & Longevity', Huberman Lab Podcast, 22 July. Available at: https://www.hubermanlab.com