Key Points:

• Real or perceived stressors can cause the hypothalamic-pituitary-adrenal (HPA) axis to release the stress hormone known as cortisol.

• In a healthy individual, cortisol will rise and fall with the sun. 

• CAR (or cortisol waking response) is the amount of cortisol secreted on waking and is a commonly accepted measure of HPA axis health.

• Cortisol and high abdominal adiposity (fat stored on the abdomen) are also known to have a cause and effect relationship.

• If an individual experiences sustained and chronic stress for long enough, the body will 'blunt' the stress response as a protection mechanism.

• There are strong connections between the hormones cortisol and insulin, as cortisol triggers the release of stored blood sugars.

• Chronic stress (cortisol) will lead to sugar dysregulation, known as Insulin Resistance.

• 'Too much' cortisol and insulin is associated with difficulty in losing weight and may cause weight gain.

• Taking up a mindfulness (meditation) practice could support weight loss efforts by positively influencing how one responds to stress and reducing the frequency of the production of cortisol.

In Brief:

Successful and sustained weight loss efforts require homeostasis or 'balance'. 

Many of our bodies most basic life-sustaining functions happen involuntarily courtesy of our prehistoric brain (such as our heart-beat, digestion and breathing). If the brain senses a threat to safety, an involuntary physiological process to produce hormones that will prepare the body to run, fight or freeze. This should not be activated day-in and day-out. 

Without a level of self-awareness, a day in modern life with what is essentially still a prehistoric brain can mean constant stress responses as we get stuck in traffic, or worry about financial stability. 

Research suggests strong connections between stress, appetite and weight gain through cortisol elevation due to the prolonged activation of the HPA axis and resulting Insulin Resistance.[1] The complex chain reactions caused by chronic stress (whether physical or psychological) wield a powerful force upon body composition.[2]

Research reviews (meta-analysis) of the effects of mindfulness on cortisol noted the limitations of the studies - relying on self-reported measures of improvement, the challenge of defining what mindfulness is or is not, and the lack of homogenous population groups for comparison.(3,8)

Overall, the effect of mindfulness practices or programmes seems to be dependent on the total hours of training, and number of sessions.[3]

In-Depth:

While the first references to mindfulness are in Buddhism, in the late 1980s, J. Kabat-Zinn introduced mindfulness training to mainstream medicine for chronically ill patients for whom conventional treatments were not working. This tool came to be known as Mindfulness-Based Stress Reduction (MSBR).

Often referred to as a practice, there is no single 'standardised' definition of mindfulness.

During practice, the person seeks to notice their feelings and emotions without reacting to them - to remain in touch with things as they are, even when things go wrong.[1] In effect, any practice aims to make the person less reactive (in this case to a stressor).

Consistency was a common theme discussed and often agreed upon - that the regularity and length of time spent practising made a difference. However, when searching the research literature, many other conclusions are conflicting. A balanced view requires looking across populations and meta-analysis (research reviews) for answers.

Many of the studies were observational, with small sample sizes and a high risk of bias. Problems such as self-selection (people who believe in the benefits are more likely to enrol) and outcome measures can be easily biased.[2]

In a 4-month study where 47 overweight or obese women were part of a mindfulness program for stress eating, although there was a moderate, non-significant effect on abdominal adiposity, it was successful in reducing anxiety and tended to reduce emotional eating.[3]

Another paper concluded that any time spent meditating significant reduces HPA activity. A novice group took part in an 8-week MBSR programme, and their results were then contrasted with a group of long term meditators (mean=264 months). The authors found that morning cortisol decreased in line with the length of experience.(3)

 

One study was designed to address common stressors for healthy working adults without a substantial time commitment, trialling at a lower 'dose' of six hour-long group sessions. While there was no significant reduction in salivary cortisol, there were significant reductions in participants perceived stress scores.[4]

 

A 2021 meta-analysis of Randomised Control Trials (the gold standard of research) acknowledged previous studies stating statistically relevant benefits of meditation on cortisol levels. They referred to the earlier work of Creswell and Lindsay (2014) postulating that they would find evidence of benefits greater for those more at-risk (people experiencing a large amount of stress or having an illness that is susceptible to stress). The review concluded that there were significant (positive) effects on those at risk for elevated cortisol levels - including for those living in stressful life situations.[5]

One such at-risk population is law enforcement officers. In another study, Officers were placed either in a control group (no intervention) or took part in an 8-week mindfulness course. Officers in the mindfulness group experienced greater reductions in salivary cortisol levels, had less burnout and sleep disturbances, and became less aggressive.[6] Importantly these benefits were not maintained when assessing participants at a follow up 3 months post-intervention. The authors suggest the need for follow-up training or 'booster' sessions to maintain training gains. 

One explanation for the disconnect in findings could be due to whether or not an individual in a study is experiencing chronic stress. With chronic stress, long term CAR can be 'blunted' - which often shows up as difficulty getting out of bed and 'getting going' in the morning. It holds to reason then that if a person was chronically stressed, a rise in morning CAR would represent an improvement. This contrasts with an individual experiencing stress (on a lower scale), who may see a reduction in their CAR. This was alluded to in the work of Christopher et al. (2018), who state 'Cortisol results suggest mindfulness may lead to reduced cortisol increase after awakening, while at the same time increasing the level at awakening. 7

 

Conclusion:

Mindfulness (which is cheap, easy to access and practice almost anywhere) shows real promise for those who experience stress physiologically.

The effect seems to rely on the total hours of training, the number of sessions and characteristics of participants such as age. While the research was conflicting in terms of reducing either salivary or blood cortisol measures, almost all acknowledged improvements in stress management scores.

If you have your nutrition and have all the other usual factors on point and are either struggling to lose weight or are even gaining weight, it might pay to incorporate a daily mindfulness practice. After all, a body in homeostasis or balance is more likely to be accommodating of the demands we place on it.

[1] Creswell, J., and Emily Lindsay. “How Does Mindfulness Training Affect Health? A Mindfulness Stress Buffering Account.” [Internet] Current Directions in Psychological Science 23 (December 1, 2014)[cited 31 Jan 2022] : 401–7. Available from:  https://doi.org/10.1177/0963721414547415.

[2] Peeke, P. M., and G. P. Chrousos. “Hypercortisolism and Obesity.” [Internet] Annals of the New York Academy of Sciences 771 (December 29, 1995)[cited 2 Feb 2022]: 665–76. Available from : https://doi.org/10.1111/j.1749-6632.1995.tb44719.x.

[3] Sanada, K., Montero-Marin, J., Diez, et al. (2016). Effects of Mindfulness-Based Interventions on Salivary Cortisol in Healthy Adults: A Meta-Analytical Review. Frontiers in Physiology [Internet], 7, Article 471 [cited 31 Jan 2022]. Available from: https://www.frontiersin.org/articles/10.3389/fphys.2016.00471/full

[4] Brand, Serge, Edith Holsboer-Trachsler, José Raúl Naranjo, et al.. “Influence of Mindfulness Practice on Cortisol and Sleep in Long-Term and Short-Term Meditators.” Neuropsychobiology [Internet] 65, no. 3 (2012) [cited 2 Feb 2022]: 109–18. Available from: https://www.researchgate.net/publication/221873645_Influence_of_Mindfulness_Practice_on_Cortisol_and_Sleep_in_Long-Term_and_Short-Term_Meditators

[5] Goyal, Madhav, Sonal Singh, Erica M. S. Sibinga, et al. “Meditation Programs for Psychological Stress and Well-Being: A Systematic Review and Meta-Analysis.” JAMA Internal Medicine [Internet] 174, no. 3 (March 1, 2014) [cited 2 Feb 2022]: 357–68. Available from https://doi.org/10.1001/jamainternmed.2013.13018.

[6] Daubenmier, Jennifer, Jean Kristeller, Frederick M. Hecht, et al. “Mindfulness Intervention for Stress Eating to Reduce Cortisol and Abdominal Fat among Overweight and Obese Women: An Exploratory Randomized Controlled Study.” [Internet] Journal of Obesity 2011 (October 2, 2011) [cited 31 Jan 2022]: e651936. https://doi.org/10.1155/2011/651936.

[7] Klatt, Maryanna D., Janet Buckworth Phd, and William B. Malarkey. “Effects of Low-Dose Mindfulness-Based Stress Reduction (MBSR-Ld) on Working Adults.”[Internet] Health Education & Behavior, 2009 [cited 31 Jan 2022], 601–14. Available from: http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.930.2939&rep=rep1&type=pdf

[8] Koncz, Adam, Zsolt Demetrovics, and Zsofia K. Takacs. “Meditation Interventions Efficiently Reduce Cortisol Levels of At-Risk Samples: A Meta-Analysis.”[Internet] Health Psychology Review 15, no. 1 (January 2, 2021)[cited 2 Feb 2022]: 56–84. Available from: https://doi.org/10.1080/17437199.2020.1760727.

[9] Christopher, Michael S., Matthew Hunsinger, Richard J. Goerling, et al. “Mindfulness-Based Resilience Training to Reduce Health Risk, Stress Reactivity, and Aggression among Law Enforcement Officers: A Feasibility and Preliminary Efficacy Trial.” [Internet] Psychiatry Research 264 (June 2018) [cited 2 Feb 2022]: 104–15. https://doi.org/10.1016/j.psychres.2018.03.059.

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