How Stress and Weight Loss Are Connected: Cortisol’s Role

Facts

• Two-thirds of the Australian and US populations are overweight or have an obesity problem
• Overweight people have reduced immune responses to vaccination and higher rate of infection
• Some weight loss products claim to work by lowering body cortisol levels
• Cortisol, the main corticosteroid hormone produced by the body upon stress, is released in a 24-hour cycle (circadian rhythm)
• This daily rhythm greatly affects your body and mental processes, including digestion and ability to fight infections
• Current research does not support a major role for cortisol in weight gain or weight loss success
• Other stresses like social isolation, sleep pattern, shift work, aging, depression can contribute to weight gain by increasing levels and altering the circadian rhythm of cortisol

Obesity

Globally, about 39% of adults are overweight and 13% are obese (11% of men and 15% of women)  (body mass index >25 kg/m²). More alarming is that more than two-thirds of the Australian and US populations are overweight.

Obesity considerably increases the risk of heart disease, diabetes and cancer.

Recent studies reveal that adults with obesity have reduced immune responses to vaccinations like the flu vaccine and higher rate of infection.

These factors should be an important consideration in developing the COVID-19 vaccine or other vaccines and national disease prevention programs.

So why do many people struggle to lose weight and keep it off?

Dieting is stressful on your body.

Within a week of reducing your calorie intake, the body undergoes many changes including hormonal changes, reductions in metabolic rate and muscle loss. The changes result in increased hunger and weight regain.

This phenomenon is called “famine reaction”.

Overweight and obese people experience famine reaction after losing as little as 8% weight loss, which is then regained within the first two years.

Cortisol and stress

Stress is the body’s response to external and internal demand or pressures, following good or bad experiences (aka “flight or fight” response).

Cortisol is produced by the body in response to stress in a pattern that follows a 24-hour cycle (circadian rhythm). So, your blood cortisol levels vary depending on the time of day.

In healthy people, cortisol levels are highest in the early morning and lowest around midnight (Figure 1).

Chronic abnormal cortisol levels can be damaging to the body

Short term or acute increase in cortisol levels can be beneficial to us.

This is often a result of psychological factors like anticipation of the day ahead, stress before exams or physical factors like exercise.

On the other hand, chronic stress causes long term elevation in blood cortisol levels.

Some studies show that moderate increase of cortisol over long periods can lead to reduced immune function, obesity, pre-diabetes, reduced memory and even heart diseases.

Cortisol and weight loss or gain

The link between cortisol and weight loss or gain is not clear based on current knowledge.

No change in cortisol levels are observed during or after weeks of calorie restriction / weight loss or in response to overeating / weight gain.

Yet, cortisol levels are not always high in overweight people. This inconsistency exists because cortisol is difficult to accurately measure.

While many dietary supplements claim to lower cortisol and enhance weight loss, no studies have shown a clear link in cortisol reduction and weight loss.

Recently, the U.S. Food and Drug Administration (FDA) approved Isturisa (osilodrostat) for adults with Cushing’s syndrome, a disease with an elevated production of cortisol.

Isturisa works by blocking cortisol production. Its effect on weight loss is not known.

Research shows that different organs each have their own circadian (24-hour) clocks. Any changes to these rhythm may have harmful effects on metabolism, immune function, and weight changes.

New research shows that how often (frequency) and when (time of day) you eat can greatly influence our circadian clocks.

Stresses like shift work, aging, sleep disturbances, social isolation, fatigue and depression can also alter cortisol circadian rhythm.

And these in turn can contribute to higher risk of obesity, heart disease, and infection.

What can you do to lower your cortisol levels, improve weight loss and reduce disease risks?

Low to moderate intensity exercises are the best method for lowering cortisol levels.

They also have the added benefit of burning calories, building muscle and promote weight loss.

Here is more information on the Functional and Clinical Significance of the 24-Hour Rhythm of Circulating corticosteroid hormones.

Author

Dr Hayley M O’Neill, PhD

Hayley is the Business Development Manager at Clueo Clinical Pty Ltd. She has over 12 years combined experience in clinical and pre-clinical research and development, and management. She was an NHMRC postdoctoral research fellow. Her expertise is metabolic diseases and weight loss. She is passionate about health and strives to improve our current knowledge to enable development of new strategies, improve patient outcomes and lower disease burden on society.

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Other articles written by this author:

• Obesity reduces vaccine effectiveness
• The power of a healthy gut