Insulin sensitivity describes how well your body responds to insulin. Good sensitivity means glucose is cleared from the blood easily. Excess abdominal fat, inactivity and poor sleep reduce it. Exercise, weight loss and sleep improve it, often within days to weeks.
- A single workout improves insulin sensitivity for up to 24–48 hours.
- Losing 5–10% of body weight markedly improves insulin resistance.
- Growth hormone, some steroids and long-term stimulant use can worsen it.
Insulin resistance sits at the centre of type 2 diabetes, fatty liver disease and many cases of difficult weight loss. The good news is that it responds quickly to lifestyle changes. Here is how it works and what improves it.
Sensitivity vs resistance
Insulin is released after meals to move glucose into cells. When cells respond well, only a small amount of insulin is needed: high sensitivity. When they respond poorly, the pancreas must make more insulin to keep blood sugar normal: insulin resistance. Over time, if the pancreas cannot keep up, blood sugar rises, leading to prediabetes and type 2 diabetes.
What causes insulin resistance
- Visceral fat: fat around the organs releases fatty acids and inflammatory signals that interfere with insulin.
- Fat in the liver and muscle
- Physical inactivity
- Poor sleep and chronic stress
- Genetics and ethnicity
- Certain medications and hormones, including corticosteroids and growth hormone
- Ageing, partly through muscle loss
Does insulin resistance stop fat loss?
People with insulin resistance can lose fat with a calorie deficit. Some find hunger harder to manage, and some feel better on lower-carbohydrate diets, but controlled trials show similar fat loss with low-carb and low-fat diets when calories and protein are matched. The real link is circular: excess fat worsens insulin resistance, and losing fat improves it.
What improves insulin sensitivity
Exercise
Muscle contraction moves glucose into cells through a pathway that does not need insulin, and a single session improves insulin sensitivity for a day or two. Both aerobic exercise and strength training help; combining them works best. Building muscle adds more storage space for glucose.
Weight loss
Losing 5–10% of body weight improves insulin sensitivity substantially and, in the Diabetes Prevention Program, reduced progression to diabetes by 58%.
Sleep
Studies show a few nights of restricted sleep reduce insulin sensitivity by around 20–25% in healthy young adults. See sleep and recovery.
Diet quality
Fibre, legumes, whole grains, fruit, vegetables, nuts and olive oil are linked with better sensitivity; sugary drinks and ultra-processed foods with worse. See balancing blood sugar.
Daily movement
Breaking up long periods of sitting with short walks lowers blood sugar and insulin after meals. See daily movement.
Hormones, drugs and insulin sensitivity
| Substance | Effect |
|---|---|
| Growth hormone and GH-releasing peptides | Reduce insulin sensitivity; raise blood sugar |
| MK-677 | Raised fasting glucose and reduced insulin sensitivity in studies |
| Corticosteroids (prednisone) | Raise blood sugar |
| Testosterone (replacement) | May improve sensitivity in men with low testosterone |
| High-dose anabolic steroids | Mixed; some studies show worse glucose tolerance |
| GLP-1 medicines | Improve blood sugar control |
See growth hormone and peptides.
A two-week insulin sensitivity reset
- Walk for 10–15 minutes after your two largest meals each day.
- Do two or three full-body strength sessions a week.
- Replace sugary drinks with water, tea or coffee.
- Build each meal around protein and vegetables, with whole-food carbohydrates.
- Aim for seven to nine hours of sleep and a consistent wake time.
- Break up sitting every 30–60 minutes with a short walk or a few squats.
Most people notice steadier energy and fewer cravings within two weeks. Blood markers such as HbA1c reflect the past two to three months, so retest after about three months to see the full effect.
Fatty liver and insulin resistance
Non-alcoholic fatty liver disease, now often called metabolic dysfunction-associated steatotic liver disease (MASLD), affects roughly one in four Canadian adults and is closely linked with insulin resistance. It often has no symptoms and may show up as mildly raised liver enzymes on bloodwork. Weight loss of 7–10% can reduce liver fat substantially. Oral anabolic steroids and alcohol add further strain to the liver.
Testing
Fasting glucose and HbA1c are the standard tests in Canada. Fasting insulin and HOMA-IR (calculated from glucose and insulin) estimate insulin resistance but are not routinely ordered and vary between labs. Waist circumference is a simple clue: over about 102 cm for men or 88 cm for women (lower thresholds for some ethnic groups) signals higher risk.
Frequently asked questions
How can I improve insulin sensitivity quickly?
Exercise improves it within hours, and better sleep within days. Losing 5–10% of body weight gives larger, lasting improvements.
Does insulin resistance make it impossible to lose weight?
No. A calorie deficit still works, and fat loss itself improves insulin resistance.
Does growth hormone affect insulin sensitivity?
Yes. Growth hormone and GH-raising peptides reduce insulin sensitivity and can raise blood sugar.
Photo: Scott Webb, StockSnap (public domain).
General information, not medical advice. Talk to your doctor about blood sugar and insulin testing.
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