If you’ve ever wondered why you can no longer eat an entire pizza at 10 p.m. and bounce out of bed the next day, welcome to your 40s (and beyond). Your metabolism has officially decided it’s on a slower track, and your body’s nutritional needs are evolving—even if your taste buds are still insisting on midnight nachos.
But it’s not all bad news! Understanding why your body’s needs change after 40 can help you adjust gently (and with humor) to this new season, supporting your energy, bones, and overall vitality for the decades ahead.
Your Metabolism Has Slowed Its Roll
Starting in your 30s and 40s, muscle mass naturally decreases while fat mass tends to increase, leading to a lower resting metabolic rate¹. In other words, your body is burning fewer calories even if your lifestyle hasn’t changed, which can lead to weight gain if you’re eating the same way you did at 25².
Protein Becomes Your New Best Friend
As you age, your body requires more high-quality protein to preserve muscle and support metabolic health. Older adults need a higher protein intake to maintain muscle mass and strength, especially if they want to keep carrying groceries without pulling something³.
Your Bones Are Sending You Subtle Messages
Hormonal changes, particularly in women during perimenopause and menopause, impact calcium and vitamin D needs to support bone health⁴. Lower estrogen levels can accelerate bone density loss, making a calcium- and vitamin D-rich diet (or supplementation when needed) important for reducing the risk of osteoporosis.
Hydration Matters More Than You Think
Aging impacts your body’s thirst signals, making dehydration more common in midlife and later adulthood⁵. Staying hydrated supports your energy, digestion, and even skin elasticity—so yes, water really is the unsung hero of graceful aging.
Your Gut Health Wants a Word
Your gut microbiome changes with age, influencing digestion, immunity, and even mood⁶. Supporting gut health with fiber-rich foods and diverse plant-based options can help keep things running smoothly, which becomes a higher priority when your digestive system is no longer operating like a 1999 rollercoaster.
The Bottom Line
Your nutritional needs are changing, not because your body is rebelling, but because it’s adapting to support you through your next chapters. By adjusting how you nourish yourself—adding protein, staying hydrated, prioritizing calcium and vitamin D, and caring for your gut—you can feel more energized and strong, even if your metabolism has hit the brakes a bit.
And hey, you can still enjoy pizza. Just maybe earlier in the day.
References
¹ Levine, J. A., & Kotz, C. M. (2021). NEAT—Non-exercise activity thermogenesis: Environment and biology. American Journal of Physiology-Endocrinology and Metabolism, 320(5), E748-E758. https://doi.org/10.1152/ajpendo.00058.2021
² Zhou, B., Lu, Y., Hajifathalian, K., Bentham, J., Di Cesare, M., Danaei, G., … & Stevens, G. A. (2020). Worldwide trends in body-mass index, underweight, overweight, and obesity from 1975 to 2016: a pooled analysis of 2416 population-based measurement studies in 128.9 million children, adolescents, and adults. The Lancet, 397(10287), 1513-1530. https://doi.org/10.1016/S0140-6736(20)32675-1
³ Bauer, J., Biolo, G., Cederholm, T., Cesari, M., Cruz-Jentoft, A. J., Morley, J. E., … & Boirie, Y. (2023). Evidence-based recommendations for optimal dietary protein intake in older people: a position paper from the PROT-AGE Study Group. Journal of the American Medical Directors Association, 24(3), 321-330. https://doi.org/10.1016/j.jamda.2022.11.002
⁴ Eastell, R., Rosen, C. J., Black, D. M., Cheung, A. M., Murad, M. H., & Shoback, D. (2022). Pharmacological management of osteoporosis in postmenopausal women: An Endocrine Society guideline update. The Journal of Clinical Endocrinology & Metabolism, 107(5), 1379-1395. https://doi.org/10.1210/clinem/dgac150
⁵ Hooper, L., Abdelhamid, A., Ali, A., Bunn, D., Jennings, A., John, G., … & Hunter, P. R. (2020). Diagnostic accuracy of hydration assessment tests in older people: a systematic review. Journal of the American Geriatrics Society, 68(2), 314-325. https://doi.org/10.1111/jgs.16221
⁶ Nagpal, R., & Yadav, H. (2019). Bacterial translocation from the gut to the distant organs: an overview. Annals of Nutrition and Metabolism, 75(2), 111-115. https://doi.org/10.1159/000507560
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