Many women in perimenopause notice their body responding to food differently. Meals that caused no issues now leave them tired or foggy. Weight accumulates around the abdomen despite no change in diet. Blood glucose readings that were normal a few years ago are edging toward "borderline." These changes reflect a hormonal metabolic shift driven primarily by the decline of estrogen.

What Insulin Resistance Means

Insulin is a hormone produced by the pancreas in response to rising blood glucose. Its job is to signal cells (particularly in the muscles, liver, and fat tissue) to absorb glucose from the bloodstream. Insulin resistance is a state in which those cells stop responding efficiently to that signal. The pancreas compensates by producing more insulin, but if the underlying resistance persists, blood glucose control gradually worsens.

Insulin resistance exists on a spectrum. At one end is normal insulin sensitivity. Further along is prediabetes (fasting glucose 100–125 mg/dL or HbA1c 5.7–6.4% using US thresholds). At the far end is type 2 diabetes. Most perimenopausal women who develop insulin resistance are somewhere in the middle of this spectrum: not at the endpoint, but trending in a direction that benefits from early intervention.

How Estrogen Protects Insulin Sensitivity

Estrogen has several direct effects on glucose metabolism. It enhances glucose uptake in skeletal muscle by increasing the expression and translocation of GLUT4, the glucose transporter that moves glucose into muscle cells.[1] It also reduces fat accumulation in the liver and suppresses hepatic glucose output.[2]

Estrogen supports pancreatic beta cell function as well. Beta cells produce insulin, and estrogen appears to protect them from stress-induced cell death while enhancing their ability to secrete insulin in proportion to glucose levels.[3]

When estrogen levels decline, all of these effects are reduced. Skeletal muscle becomes less efficient at absorbing glucose, and the liver tends toward greater glucose production. Beta cell function may deteriorate over time if the metabolic environment remains unfavourable, a process that unfolds gradually, independently of any changes in diet or exercise habits.

The SWAN Study Evidence

The Study of Women's Health Across the Nation (SWAN), one of the largest longitudinal studies of midlife women, tracked metabolic changes across the menopausal transition in a diverse cohort. SWAN data showed insulin resistance increased after menopause, independent of changes in weight or BMI.[4] The metabolic change is driven by the hormonal transition itself, not solely by lifestyle factors.

Additional SWAN analyses found that women who experienced greater estrogen fluctuations during perimenopause had more variable glucose metabolism, consistent with the idea that estrogen's stabilising effect on insulin sensitivity is dose-dependent and responsive to hormonal fluctuation.[5]

The Visceral Fat Connection

Estrogen influences where fat is stored. During the reproductive years, estrogen promotes fat storage in subcutaneous depots (under the skin at the hips, thighs, and buttocks). As estrogen declines, fat preferentially redistributes to visceral depots around the abdominal organs.[6]

Visceral fat is metabolically active in a way subcutaneous fat is not. It releases free fatty acids and inflammatory cytokines directly into the portal circulation that feeds the liver, driving hepatic insulin resistance. Visceral fat also produces adipokines like resistin and adiponectin in altered proportions that worsen whole-body insulin sensitivity.[7]

Waist circumference, not just total weight, is therefore the more useful midlife metric. A waist measurement above 88 cm (35 inches) is associated with elevated cardiometabolic risk and is a reasonable flag for discussing metabolic assessment with a GP, regardless of total body weight.[8]

Practical Levers

Resistance training

Skeletal muscle is the largest site of glucose disposal in the body. The more muscle mass you have, and the more metabolically active it is, the more glucose can be cleared from the blood after meals without relying on high insulin output. Resistance training increases GLUT4 expression in muscle cells independently of insulin, so glucose uptake improves even with reduced insulin sensitivity.[9]

A systematic review by Strasser et al. (2010) found that resistance training alone improved fasting blood glucose and HbA1c in people with insulin resistance and type 2 diabetes.[10] For perimenopausal women without diagnosed metabolic conditions, the effect is likely more modest but still present.

Practical dose: 2–3 sessions per week targeting major muscle groups. Compound movements (squats, deadlifts, rows, presses) engage the largest muscle groups and produce the most metabolic benefit per unit of time.

Carbohydrate quality, not carbohydrate elimination

Low-carbohydrate diets reduce glucose exposure and can improve insulin sensitivity acutely, but they are not necessary for everyone. What the evidence supports more consistently is prioritising carbohydrate quality: minimising refined, rapidly absorbed carbohydrates (white bread, sugary drinks, processed cereals) in favour of whole foods with higher fibre content, which slow glucose absorption and reduce postprandial insulin spikes.[11]

Soluble fibre from oats, legumes, and fruit reduces the rate of glucose absorption from the gut and feeds gut bacteria that produce short-chain fatty acids, which improve insulin sensitivity through independent pathways.[12]

Sleep

The connection between sleep and insulin resistance is bidirectional. One night of partial sleep deprivation (4–5 hours) reduces insulin sensitivity in healthy adults by approximately 25–30% compared to a full night of sleep.[13] For women whose sleep is already disrupted by vasomotor symptoms, this compounds metabolic disruption that is already in progress. Treating night sweats and improving sleep quality is a metabolic intervention as well as a quality-of-life one.

Protein distribution

Spreading protein intake across meals rather than concentrating it in the evening improves muscle protein synthesis and supports muscle mass maintenance.[14] Since muscle mass supports glucose disposal, protein distribution matters for metabolic health beyond body composition goals. Aiming for 25–35g of protein per meal (rather than a protein-light breakfast and a protein-heavy dinner) is a practical target.

HRT and Glucose Metabolism

Systemic HRT, particularly transdermal estrogen, has been shown in clinical trials and observational studies to improve insulin sensitivity in postmenopausal women.[15] A meta-analysis by Mauvais-Jarvis et al. (2017) found that transdermal estradiol was associated with improved glucose tolerance and reduced fasting insulin compared to placebo, with the oral route showing less consistent effects, likely because oral estrogen affects hepatic metabolism in ways that can offset some metabolic benefits.[3]

Improved metabolic health is not the primary indication for HRT, but it is a documented secondary benefit for many women, particularly when transdermal estrogen is used.

Assessing Your Metabolic Risk

If you are concerned about insulin resistance, a basic metabolic panel is the starting point. Request:

  • Fasting blood glucose (target below 100 mg/dL / 5.5 mmol/L)
  • HbA1c (target below 5.7% / 39 mmol/mol)
  • Fasting insulin (allows calculation of HOMA-IR, a measure of insulin resistance)
  • Waist circumference measurement

These are not routinely offered at every annual check, but they are straightforward to request and are covered by NHS health checks for those eligible (ages 40–74 in England). Identifying metabolic drift early, before fasting glucose crosses into prediabetes range, keeps the full range of lifestyle and clinical options open; catching it at that stage, the trajectory is genuinely reversible.

References

[1] Barros, R. P., Gustafsson, J. A. (2011). Estrogen receptors and the metabolic network. Cell Metabolism, 14(3), 289–299. https://doi.org/10.1016/j.cmet.2011.08.005

[2] Riant, E., Waget, A., Cogo, H., Arnal, J. F., Burcelin, R., Gourdy, P. (2009). Estrogens protect against high-fat diet-induced insulin resistance and glucose intolerance in mice. Endocrinology, 150(5), 2109–2117. https://doi.org/10.1210/en.2008-0971

[3] Mauvais-Jarvis, F., Clegg, D. J., Hevener, A. L. (2013). The role of estrogens in control of energy balance and glucose homeostasis. Endocrine Reviews, 34(3), 309–338. https://doi.org/10.1210/er.2012-1055

[4] Derby, C. A., Crawford, S. L., Pasternak, R. C., Sowers, M., Sternfeld, B., Matthews, K. A. (2009). Lipid changes during the menopause transition in relation to age and weight: The Study of Women's Health Across the Nation. American Journal of Epidemiology, 169(11), 1352–1361. https://doi.org/10.1093/aje/kwp043

[5] Sowers, M. R., Wildman, R. P., Mancuso, P., et al. (2008). Change in adipocytokines and ghrelin with menopause. Maturitas, 59(2), 149–157. https://doi.org/10.1016/j.maturitas.2007.12.006

[6] Tchernof, A., Desmeules, A., Richard, C., et al. (2004). Ovarian hormone status and abdominal visceral adipose tissue metabolism. Journal of Clinical Endocrinology and Metabolism, 89(7), 3425–3430. https://doi.org/10.1210/jc.2003-031561

[7] Kershaw, E. E., Flier, J. S. (2004). Adipose tissue as an endocrine organ. Journal of Clinical Endocrinology and Metabolism, 89(6), 2548–2556. https://doi.org/10.1210/jc.2004-0395

[8] Lean, M. E., Han, T. S., Morrison, C. E. (1995). Waist circumference as a measure for indicating need for weight management. BMJ, 311(6998), 158–161. https://doi.org/10.1136/bmj.311.6998.158

[9] Holten, M. K., Zacho, M., Gaster, M., Juel, C., Wojtaszewski, J. F., Dela, F. (2004). Strength training increases insulin-mediated glucose uptake, GLUT4 content, and insulin signaling in skeletal muscle in patients with type 2 diabetes. Diabetes, 53(2), 294–305. https://doi.org/10.2337/diabetes.53.2.294

[10] Strasser, B., Siebert, U., Schobersberger, W. (2010). Resistance training in the treatment of the metabolic syndrome: A systematic review and meta-analysis of the effect of resistance training on metabolic clustering in patients with abnormal glucose metabolism. Sports Medicine, 40(5), 397–415. https://doi.org/10.2165/11531380-000000000-00000

[11] Livesey, G., Taylor, R., Livesey, H. F., et al. (2019). Dietary glycemic index and load and the risk of type 2 diabetes: A systematic review and updated meta-analyses of prospective cohort studies. Nutrients, 11(6), 1280. https://doi.org/10.3390/nu11061280

[12] Koh, A., De Vadder, F., Kovatcheva-Datchary, P., Backhed, F. (2016). From dietary fiber to host physiology: Short-chain fatty acids as key bacterial metabolites. Cell, 165(6), 1332–1345. https://doi.org/10.1016/j.cell.2016.05.041

[13] Spiegel, K., Leproult, R., Van Cauter, E. (1999). Impact of sleep debt on metabolic and endocrine function. Lancet, 354(9188), 1435–1439. https://doi.org/10.1016/S0140-6736(99)01376-8

[14] Areta, J. L., Burke, L. M., Ross, M. L., et al. (2013). Timing and distribution of protein ingestion during prolonged recovery from resistance exercise alters myofibrillar protein synthesis. Journal of Physiology, 591(9), 2319–2331. https://doi.org/10.1113/jphysiol.2012.244897

[15] Salpeter, S. R., Walsh, J. M., Ormiston, T. M., Greyber, E., Buckley, N. S., Salpeter, E. E. (2006). Meta-analysis: Effect of hormone-replacement therapy on components of the metabolic syndrome in postmenopausal women. Diabetes, Obesity and Metabolism, 8(5), 538–554. https://doi.org/10.1111/j.1463-1326.2005.00545.x