Thyroid Conditions and Weight: What Canadians Should Know
An underactive thyroid can add a few kilograms and leave you exhausted. Treating it helps, but thyroid hormone is not a fat-loss tool for everyone else.
SteroidsCanada.org editorial teamUpdated · 2 min read
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The thyroid is a small gland in the neck that sets the pace for much of your metabolism. When it makes too little hormone, everything slows; too much, and everything speeds up. Thyroid problems are common in Canada and are frequently blamed, sometimes correctly, for weight changes.
How thyroid hormone affects weight
Thyroid hormones (T4 and its active form, T3) influence how much energy your body burns at rest, how warm you feel and how fast your heart beats. The brain controls the gland through thyroid-stimulating hormone (TSH). When thyroid output falls, TSH rises to push it harder, which is why TSH is the main screening test.
Underactive (hypothyroidism)
- Fatigue, feeling cold
- Modest weight gain, puffiness
- Constipation, dry skin, hair thinning
- Low mood, slower thinking
Overactive (hyperthyroidism)
- Weight loss despite eating more
- Racing heart, anxiety, tremor
- Heat intolerance, sweating
- Poor sleep, muscle weakness
Getting tested
Ask your doctor for a TSH test if you have several symptoms above. If TSH is abnormal, free T4 (and sometimes T3 and thyroid antibodies) clarifies the picture. Results can be affected by biotin supplements, so stop biotin a couple of days before testing, and by recent illness.
Treatment
Hypothyroidism is usually treated with levothyroxine, a synthetic T4 taken once a day on an empty stomach. The dose is adjusted every six to eight weeks until TSH is in range. Hyperthyroidism is treated with medicines that slow the gland, radioactive iodine or surgery, depending on the cause.
Once treated, energy usually returns and the fluid-related weight settles. Further fat loss still depends on diet and activity, the same as for anyone else.
Thyroid hormone as a “diet drug”
T3 and T4 products are sometimes used for fat loss by people with normal thyroid function. Pushing thyroid hormone above normal does increase calorie burn, but it also:
- breaks down muscle protein as well as fat;
- raises heart rate and the risk of atrial fibrillation;
- accelerates bone loss over time;
- can cause anxiety, insomnia and heat intolerance;
- suppresses your own thyroid, which needs time to recover after stopping.
Eating and training with a thyroid condition
- Take levothyroxine consistently, apart from calcium, iron and coffee, which reduce absorption.
- Set calories from your actual weight trend, not from equations alone; the macro calculator is a starting point you can adjust.
- Prioritise protein and strength training to keep muscle.
- Allow time: once treated, metabolism usually returns to normal within a few months.
Thyroid problems in men who train
Men are less likely to be tested for thyroid problems, yet hypothyroidism can mimic low testosterone: fatigue, low libido, weight gain and low mood. If you are investigating low testosterone, ask whether TSH has been checked as well. Some anabolic steroids lower thyroid-binding proteins and change thyroid test results, so tell your doctor about any compounds you use before tests are interpreted.
Canadian resources
The Thyroid Foundation of Canada offers patient information and support groups. Your family doctor can manage most thyroid conditions and refer to an endocrinologist when needed. Provincial health plans cover thyroid blood tests ordered by a physician.
Questions
How much weight does hypothyroidism add?
Typically a few kilograms, often 2 to 5, much of it salt and water. Large weight gains usually have other causes too.
Will treatment make me lose weight?
Treatment usually removes the fluid-related gain and restores energy, which makes other changes easier. It rarely causes large weight loss by itself.
Is hypothyroidism common in Canada?
Yes. It is one of the most common hormone conditions, especially in women and older adults.
Can I take thyroid medication to lose fat?
Not safely without a deficiency. Excess thyroid hormone breaks down muscle as well as fat and strains the heart and bones.
Sources
General information, not medical advice. Written for adults in Canada. Anabolic steroids are Schedule IV under the Controlled Drugs and Substances Act. Talk to a licensed healthcare provider and get bloodwork before using any compound.
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