Losing weight is always challenging, and obtaining a lasting weight loss is often difficult for many people.
People with hypothyroidism (low thyroid function) have even more difficulty losing weight as they burn fewer calories than people with good thyroid function.
The thyroid gland secretes thyroid hormones which control metabolism and thus the conversion of the food we eat to carbon dioxide, water, and energy.
Low thyroid function often leads to weight gain, as well as a whole range of other symptoms, because the cells of the body are not producing enough energy.
Measuring Thyroid Function
You can actually be hypothyroid and have normal blood tests for thyroid function. Blood tests do not necessarily give you the whole picture of what is going on at the cellular level. In addition, the normal ranges for thyroid blood tests have been made very broad, so you might fall within the normal range on a blood test but still be low thyroid. My book Test Your Thyroid Function explains how to assess your actual metabolic status more fully.
Test Your Thyroid Function Using Pulse and Temperature
You can use the home thyroid test described in my book Test Your Thyroid Function to measure your actual thyroid function on the cellular level. This test is based on body temperature and pulse rate as well as symptoms. According to Dr. Ray Peat and Broda O. Barnes M.D., this is a reliable way of measuring the actual metabolic rate on the cellular level.
Weight Gain and Inflammation
Weight gain and inability to lose weight are generally caused by hypothyroidism and chronic inflammatory processes.
If you have a low metabolic rate and a high level of general inflammation, it becomes almost impossible to lose weight, even on the strictest diet. Chronic inflammatory processes suppress metabolism and lead to weight gain as well as water retention and many other chronic degenerative conditions.
How to Obtain a Lasting Weight Loss
My approach to weight loss is different from just focusing on calorie restriction. My health approach is based on a deep biochemical understanding of how the body works on the cellular level.
My diet and health recommendations promote good thyroid function and metabolism as well as a healthy hormonal balance, with low levels of inflammatory markers and high levels of protective anti-stress hormones, thereby supporting a lasting weight loss. You can find the full approach in my book How to Boost Metabolism with Food and my Metabolic Nutrition Mastery course.
Weight Loss and Thyroid Medication
If you have low thyroid function you need to be on a thyroid-promoting diet as well as use a good thyroid replacement therapy in order to lose weight.
The right kind of thyroid medication is essential for successful weight loss. It is necessary that your thyroid replacement therapy contains both of the thyroid hormones, meaning T4 and T3 — either in the form of reliable prescription thyroid medication or a good over-the-counter natural desiccated thyroid supplement. My book How to Use Thyroid Medication covers how to navigate these options.
In my consultation service, I help people use the right kind of thyroid replacement therapy customised to their individual situation. You can also use my Thyroid Recovery & Renewal course for a structured self-guided programme.
Why Starches Promote Weight Gain
Pure starch overstimulates insulin production, which leads to low blood sugar. Low blood sugar inhibits the activation of the storage thyroid hormone T4 to the active thyroid hormone T3.
In addition, the overstimulation of insulin by starches promotes fat synthesis, and starches thereby strongly promote weight gain.
In contrast, the fructose part of normal table sugar, honey, and the sugar in fruits prevents the overstimulation of insulin and helps the liver store glycogen, which stabilises the blood sugar.
A stable blood sugar helps your body activate your thyroid hormone and thus burn more calories. It has been found that you can increase your metabolic rate by 25% by excluding starches and instead adding sugar, honey, and fruit to your diet.
Frequently Asked Questions
Why is it so hard to lose weight with hypothyroidism?
People with low thyroid function burn fewer calories than those with good thyroid function, because the cells are not producing enough energy. On top of that, the chronic inflammation associated with hypothyroidism suppresses metabolism further and causes water retention. This means the usual approach of calorie restriction fails — the body simply slows down further to compensate. Addressing the underlying thyroid function and inflammation is what creates lasting results.
Can I be hypothyroid even if my blood tests are normal?
Yes — the normal ranges for thyroid blood tests are very broad, meaning many people who genuinely suffer from low thyroid function fall within the "normal" range. Blood tests also reflect circulating hormone levels, not necessarily what is happening at the cellular level. The home thyroid test — measuring body temperature and resting pulse rate — provides a much more direct picture of actual metabolic rate. I explain this in detail in my book Test Your Thyroid Function.
Why does replacing starches with fruit help with weight loss?
Starchy foods cause a rapid rise in insulin, which drives blood sugar down and suppresses the conversion of T4 to T3 — the active thyroid hormone. The fruit sugar fructose, on the other hand, does not trigger the same insulin spike and instead helps the liver store glycogen, stabilising blood sugar. A stable blood sugar reduces stress hormones and supports thyroid activation, which can increase metabolic rate by around 25%. I cover this in my book How to Boost Metabolism with Food.
Do I need thyroid medication to lose weight with hypothyroidism?
If your thyroid function is significantly low, diet alone may not be enough to restore your metabolic rate sufficiently for sustained weight loss. In those cases, the right thyroid replacement therapy — containing both T4 and T3 — is an important part of the picture. Diet, supplements, and thyroid medication work best together. I cover how to combine these in my book How to Use Thyroid Medication and my Thyroid Recovery & Renewal course.
