If you have been struggling to lose weight despite eating well and exercising, you are not alone. Millions of people find themselves in the frustrating position of doing "everything right" yet watching the scales refuse to budge — or worse, continue to climb.
While calories and activity certainly matter, they are not the complete picture. Hormones — the chemical messengers that regulate virtually every bodily function — play a profound role in weight management. When hormones are out of balance, losing weight can feel nearly impossible, regardless of how hard you try.
The good news is that blood tests can identify hormonal imbalances that may be sabotaging your weight loss efforts, allowing for targeted treatment.
The Hormonal Weight Connection
Your body weight is regulated by a complex network of hormones that influence:
When these hormones are functioning optimally, weight management is relatively straightforward. When they are imbalanced, it can feel like your body is working against you.
Thyroid Hormones: The Metabolism Master
The thyroid gland produces hormones that regulate your metabolic rate — how quickly you burn calories at rest. Thyroid dysfunction is one of the most common hormonal causes of weight problems.
### Hypothyroidism (Underactive Thyroid)
When the thyroid produces insufficient hormones, metabolism slows significantly.
Effects on weight:
Other symptoms:
Blood tests: TSH, Free T4, Free T3, thyroid antibodies. For comprehensive information, read our guide to private blood tests for thyroid problems.
### Subclinical Hypothyroidism
Some people have thyroid function in the "normal" range but at the lower end, which may still affect metabolism. This subclinical hypothyroidism can make weight loss more difficult.
Insulin: The Fat Storage Hormone
Insulin is released by the pancreas to help cells absorb glucose from the blood. However, insulin also promotes fat storage and inhibits fat burning.
### Insulin Resistance
When cells become less responsive to insulin, the body produces more to compensate. High insulin levels promote weight gain, particularly around the abdomen.
Effects on weight:
Signs of insulin resistance:
Blood tests: Fasting insulin, fasting glucose, HbA1c, HOMA-IR calculation. For more information, read our guide to understanding the A1C blood test.
Cortisol: The Stress Hormone
Cortisol is released in response to stress. While essential for survival, chronically elevated cortisol wreaks havoc on weight.
Effects on weight:
Signs of cortisol imbalance:
Blood tests: Morning cortisol, DHEA-S. For detailed information, read our article on the link between stress, cortisol, and your blood test results.
Sex Hormones
### Oestrogen
Oestrogen influences where fat is stored and helps regulate appetite. Both high and low oestrogen can contribute to weight gain.
Low oestrogen (menopause):
High oestrogen (oestrogen dominance):
### Testosterone
In both men and women, testosterone helps maintain muscle mass, which is essential for metabolic rate.
Low testosterone effects:
### Progesterone
Low progesterone can contribute to oestrogen dominance and affect sleep quality, indirectly impacting weight.
For more information, read our article on hormone imbalance symptoms you should not ignore.
Other Hormones Affecting Weight
### Leptin
Leptin is produced by fat cells and signals fullness to the brain. In obesity, leptin resistance develops, meaning the brain no longer responds to these signals.
### Ghrelin
Ghrelin is the "hunger hormone." Sleep deprivation increases ghrelin, leading to increased appetite.
### Growth Hormone
Growth hormone helps maintain muscle mass and promotes fat burning. Levels decline with age and poor sleep.
Creating a Hormone Weight Panel
A comprehensive hormone assessment for weight issues should include:
For a complete overview, read our guide to what's included in a comprehensive health check.
Taking Action
If blood tests reveal hormonal imbalances:
Hormone Testing in London
At Private Blood Tests London, we offer comprehensive hormone panels at our CQC-registered clinic in South Kensington. Our tests can reveal whether hormonal imbalances are contributing to your weight struggles, giving you the information you need to take targeted action.
Explore our [thyroid function tests](/thyroid-test), [diabetes screening](/diabetes-test), and [comprehensive health checks](/health-screening) for a complete metabolic assessment.
Stop fighting your body. Understand it. Book your hormone blood test today.