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Toronto Functional Medicine Approach to Leptin, Thyroid Health and Weight Loss


If you think crash dieting is the only way to lose weight, our functional medicine Toronto team disagrees!

A crash diet rapidly sheds pounds on the person who’s dieting, but it could set in motion unwanted chronic symptoms, like digestive issues. In fact, changes could occur to the hormones that help regulate satiety, appetite and hunger, which include leptin, ghrelin and thyroid hormones. 

If you’re trying to lose weight, have you considered seeking help from your healthcare providers? This is because it is not as simple as black and white – sometimes there could be underlying issues preventing you from reaching your  wellness goal.

Untreated thyroid issues, especially if you have thyroid malfunctions, such as Hashimoto’s thyroiditis, a goiter (enlarged thyroid), and thyroid nodules is also a factor. These issues could cause the low release of thyroid hormones and slow down metabolism. When your thyroid is not producing enough thyroid hormones, this can trigger other inconvenient symptoms too, such as excessive fatigue and irritability.

Recommended Reading: Recharging Your Thyroid with Functional Medicine from Toronto

Additionally, leptin resistance could also contribute to the problem; this is when the body loses sensitivity to leptin (the hormone related to the hunger sensation). When leptin resistance occurs, the hunger feeling is always switched “on”. To help conserve energy under leptin resistance, your brain automatically tells the body to decrease energy levels, which means you require less calories because you’re using less energy. Leptin resistance, therefore, could contribute to obesity because the hunger sense is endlessly “on” while your body operates under low metabolism. 

So what’s the link between leptin and your thyroid ? Our clinical practice, the Toronto Functional Medicine Centre, discusses how leptin works, its connection to the thyroid, and why hormone imbalances could break your weight-loss triumphs.

How does leptin operate in the body?

Leptin is like a messenger, which tells your hypothalamus when fat cells are full or hungry. When leptin levels are optimal, your brain knows when you’ve eaten enough food for energy expenditure. But when your body lacks leptin, you could continue to feel hungry when you’re not supposed to eat!

Leptin resistance affects how you lose weight. It happens when your body makes excessive amounts of leptin due to additional fat cells formed in the body. “Because fat cells produce leptin in proportion to their size, people with obesity [may] also have very high levels of leptin,” notes Healthline. When leptin resistance arises, it tells you to keep eating despite there being enough leptin in the fat cells. Thus, overeating and extra pounds on the body could result. 

Uncovering leptin’s relationship with your thyroid

Leptin levels affect thyroid health, too. The hypothalamic-pituitary-adrenal axis (HPA axis) is one of the body systems that acts as a pathway between the hypothalamus, pituitary gland and adrenals. Under healthy conditions, leptin incites the hypothalamus to intensely communicate along the axis, which results in optimal metabolism and energy, and restricts food intake when it’s not needed. Meanwhile, leptin is directed towards the hypothalamus to regulate consumed food for energy. 

Under unhealthful body conditions, leptin cannot optimally function, so you end up lacking important metabolic support. When leptin resistance occurs, the body interprets this as a feeling of “starvation”. Rather than flush excess fat, the body ends up increasing fat cells to accommodate that “starvation”, while releasing enzymes that either activate or inactivate thyroid hormones. This could cause an imbalance of thyroid T3 and TSH hormones, which are needed for optimal  metabolism functioning. 

Leptin resistance truly affects the regulation of thyroid hormone signaling and can trigger weight gain. This also goes for when you have hypothyroidism – leptin resistance and being overweight can trigger thyroid hormone imbalances. Between wonky thyroid hormones and leptin resistance, the body undergoes a vicious sequence of inflammation and excess weight. After all, obesity can lead to leptin resistance, and leptin resistance can lead to obesity! So if you’re battling weight gain and hypothyroidism, focusing on leptin levels could help. 

(FYI: Having trouble shedding pounds? You should know that when leptin levels are above normal, this could lead to the low functioning of intracellular thyroid hormones. This decreases the metabolic rate and prompts weight gain, especially with elevated levels of reverse T3.) 

Accordingly, we advise speaking to an integrative and functional medicine healthcare provider who can assist with reversing your leptin resistance; this could contribute to weight loss and repair damage to your HPA axis. With an evidence-based approach, a functional medicine practitioner can determine which lab tests are suitable for pinpointing what’s going on in the body. And since the functional medicine approach to wellness embraces individuality, a treatment plan can be personalized for your health needs. Some of the natural treatment options for alleviating leptin resistance may include: 

  • Changes to lifestyle factors: discover innovative, natural ways to reduce inflammation, such as relieving stress through mindfulness and meditation, and increasing physical activity.  
  • Dietary changes: reduce your sugar intake, consume more protein, eat non-processed food that’s graded low on the glycemic index; follow guidelines for an anti-inflammatory or paleo diet; increase soluble fibre to improve the your gut microbiome and lessen insulin spikes; reduce carbohydrates to cut down high levels of triglycerides. 
  • Sleep modifications: improving sleep quality could help alleviate leptin resistance; if there are concerns with nutritional deficiencies, lab tests could disclose which nutrients you’re lacking and how this affects your sleep. 
  • Supplementation: L-cysteine and kaempferol are a few supplements that may be suggested. L-cysteine is an amino acid that could help curb feelings of hunger; kaempferol, an antioxidant based in fruits and vegetables, could help lessen high levels of TSH while increasing the intracellular enzyme that activates T3.

Are you inspired to recharge your life with functional medicine strategies? Then let’s talk! Our private practice could provide you with new insights and comprehensive care for losing weight. Let’s introduce you to a personalized approach to wellness.

How to get clinical care for weight loss 

By becoming a patient at the Toronto Functional Medicine Centre, you can have access to a wide variety of treatment modalities, including naturopathic care, allopathic medicine, Traditional Chinese Medicine, clinical nutrition and accessible functional medicine testing. 

Our integrative approach to wellness is applicable for in-person visits and virtual consultations, for both chronic and acute health issues. Treatment plans can be catered for different health issues, such as abdominal pains, digestive issues, nutritional deficiencies, infertility, brain fog, and other concerns. Let’s unravel the root cause of your chronic symptoms and uncover healthy ways to reach optimal functioning.

What would happen if we focused on leptin levels and thyroid health to help you lose weight? Click here to contact us for a DISCOVERY SESSION on functional medicine in Toronto. 

Disclaimer: The information in this article is designed for educational purposes only and is not intended to be a substitute for informed medical advice or care. This information should not be used to diagnose or treat any health problems or illnesses without consulting a doctor. Consult with a health care practitioner before relying on any information in this article or on this website.


Duntas LH, Biondi B. The Interconnections Between Obesity, Thyroid Function, and Autoimmunity: The Multifold Role of Leptin. Thyroid (2013) 23(6):646–53. doi: 10.1089/thy.2011.0499

Flier, J S et al. “Leptin, nutrition, and the thyroid: the why, the wherefore, and the wiring.” The Journal of clinical investigation vol. 105,7 (2000): 859-61. doi:10.1172/JCI9725

Leptin and Leptin Resistance: Everything You Need to Know”, Written by Kris Gunnars, BSc — Updated on January 19, 2022, Healthline, viewed on June 18, 2022. 

Oliveira, K. J., Chiamolera, M. I., Giannocco, G., Pazos-Moura, C. C., & Ortiga-Carvalho, T. M. (2019). Thyroid function disruptors: from nature to chemicals, Journal of Molecular Endocrinology, 62(1), R1-R19. Retrieved Jun 18, 2022, from

Sheng JA, Bales NJ, Myers SA, et al. The Hypothalamic-Pituitary-Adrenal Axis: Development, Programming Actions of Hormones, and Maternal-Fetal Interactions. Front Behav Neurosci. 2021;14:601939. Published 2021 Jan 13. doi:10.3389/fnbeh.2020.601939

The Facts on Leptin: FAQ” ,” by Keri Wiginton, reviewed by Sabrina Felson, MD on May 19, 2022, viewed on June 18, 2022. 


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