Understanding Midlife Weight Gain: Four Key Factors

By Kari Sherman and Dr Andy Pullen, GP

Are you noticing a bit more around the waistline as the years go by? You’re not alone. Weight gain in midlife is a common experience, and it’s influenced by a blend of natural changes and lifestyle shifts. Many of my Pilates clients tell me they feel frustrated by weight gain that seems harder to shift as they reach their forties and beyond. With insights from my partner, Dr. Andy, and the feedback from so many of you, we’re here to break down the four key reasons behind midlife weight gain. Plus, we’ll share how incorporating Pilates can be a game-changer for maintaining a strong, flexible, and healthy body through these years.

Let’s explore four major factors that often contribute to midlife weight gain and, ultimately, how you can manage them.

Muscle Loss Starting from Age 35-40

I used to be able to go on holiday, indulge a bit, and then easily get back into shape with a few adjustments. But everything changed around forty. Muscle mass naturally begins to decline between ages 35 and 40, a process known as sarcopenia. This loss impacts our metabolism because muscle burns more calories than fat, even at rest. Unfortunately, a decrease in muscle mass can lead to a slower metabolic rate, contributing to weight gain over time.

Research shows that adults typically lose about 3-8% of their muscle mass per decade after the age of 30, with this decline accelerating after age 60 (Ref 1). Engaging in regular resistance training such as weight lifting, bodyweight exercises, or Pilates can slow down or even counteract muscle loss. (Did you think I wasn’t going to mention Pilates?!) By maintaining muscle mass, resistance training supports a healthier metabolism, which is essential for managing weight as we age (Ref 2).

As we weave lunges, planks, and press-ups into our Pilates classes, next month we’ll take a deeper dive into sarcopenia and more specific ways you can address it.

Less Active as We Age

Do you ever look at people in their 20s and wish you had their energy?! Or do you find that your full day takes more out of you than it used to? It might not just be because "age is slowing you down."

Physical activity often decreases as we age due to lifestyle changes, family and work commitments, or physical limitations. Studies show that adults typically reduce their physical activity by 10% each decade, leading to reduced energy expenditure and potential weight gain (Ref 3).

What physical limitations might come into play? Common factors include joint pain or arthritis, reduced flexibility, chronic conditions such as back pain, osteoporosis, or diabetes, past injuries, and balance or coordination issues. These limitations can make activities you once loved feel riskier. Does this sound familiar? I see it every day in my Pilates studio, but I also witness the benefits that movement and lifestyle adjustments can bring!

Maintaining an active lifestyle is essential as we age. Finding activities you enjoy like walking, gardening, cycling, and regular Pilates, can make a meaningful difference in managing weight and supporting overall health (Ref 4).

Dietary Changes with Lifestyle Shifts

Dietary habits often change in midlife. Increased stress (any hands up for teenagers?!), more disposable income, and greater access to social activities can lead to eating and drinking changes. Personally, I feel I travel more and, of course, feel compelled to try every local cuisine, and quality time with friends and family is often centred around food and drink. I’m not alone; many mid-lifers report larger portions, more processed foods, and more alcohol, which can all contribute to weight gain.

Additionally, stress can trigger emotional eating, leading to poor food choices. A study published in the American Journal of Clinical Nutrition found that people often turn to comfort foods when stressed, which disrupts a balanced diet and adds extra calories (Reference 5).

With so many opinions, diets, and debates on social media, we’ll break down the impact of dietary changes on health and waistlines in January, along with some meal planning tips and recipes.  Until then, consider your portion sizes, choose more protein and vegetables at meal times and think about all the snacks in-between meal time. 

Hormonal Changes

Hormonal fluctuations also play a big role in midlife weight gain. For women, menopause brings a drop in oestrogen, often causing fat to concentrate around the waist. In men, testosterone levels decline, leading to the dreaded tummy bulge—particularly in those who are less active or carrying extra weight.

Maintaining a healthy diet, regular exercise, and managing stress can help alleviate the effects of these hormonal changes. In March, we’ll explore the effects of menopause on women, along with the pros and cons of hormone replacement therapy; a topic that I sometimes find confusing!

Weight gain in midlife can feel frustrating, but understanding the "why" behind it is the first step toward taking control. It’s all about making small, consistent changes that fit your lifestyle, staying active, and giving yourself grace along the way. Simple actions like adding regular walks, prioritising strength-building exercises, and being mindful of portion sizes can make a meaningful difference. Pilates can be an incredible ally on this journey, helping you build strength, improve flexibility, and maintain a healthy weight. We’re all in this together, and with a little knowledge, movement, and balanced choices, you can feel stronger, healthier, and more confident.

References

1. Wolfe, R. R. (2006). The Underappreciated Role of Muscle in Health and Disease. American Journal of Clinical Nutrition, 84(3), 475-482.
2. Phillips, S. M., & Winett, R. A. (2010). Uncomplicated Resistance Training and Health-Related Outcomes: Evidence for a Public Health Mandate. Current Sports Medicine Reports, 9(4), 208-213.
3. Booth, F. W., Roberts, C. K., & Laye, M. J. (2012). Lack of Exercise Is a Major Cause of Chronic Diseases. Comprehensive Physiology, 2(2), 1143-1211.
4. Physical Activity Guidelines Advisory Committee Report, 2018. U.S. Department of Health and Human Services.
5. Michaud, D. S., et al. (1990). Eating Behavior in Stressful Situations: A Behavioral and Nutritional Evaluation. American Journal of Clinical Nutrition, 51(4), 704-709.