Cortisol , Stress & Obesity (DP IB Psychology): Revision Note

The cortisol-awakening response (CAR)

• Cortisol is a hormone produced in the adrenal cortex via activation of the hypothalamus-pituitary-adrenal (HPA) axis when the body is exposed to stress

• The immune system (mainly white blood cells) defends the body against harmful antigens such as bacteria, viruses, and cancerous cells

• Cortisol normally helps by regulating the immune system and suppressing inflammation, which is usually beneficial

• However, under chronic stress, excess cortisol builds up in the bloodstream:

  • This leads to over-suppression of the immune system

    • As a result, the body’s resistance to illness is lowered

• Stress does not directly cause infection, but it reduces the immune system’s ability to fight antigens, making infections more likely

• This explains why many people often develop colds or minor illnesses during exam periods, when stress levels (and cortisol) are high

Obesity & stress

• Stress can lead to obesity, and obesity can increase stress levels – it is a two-way relationship

• Stress affects self-regulation

  • Stress reduces people’s ability to control their behaviour (e.g., resisting fatty, sugary foods)

• Stress disrupts eating-related hormones and peptides:

  • Leptin – signals fullness to the brain

  • Ghrelin – signals hunger

  • Neuropeptide Y – regulates appetite

• Disruption to these hormones makes overeating more likely under stress

Research support for cortisol, stress & obesity

Kumar et al. (2022)

Aim:

• To examine the link between stress and obesity

Method:

• A literature review of journal articles on stress, cortisol and obesity published between 2000 and 2020

Results:

• Obesity treatment is more effective if stress is targeted

• Stress is a major factor in obesity (though biological and sociocultural factors also play a role)

• Research shows people eat more under stress due to the CAR

• Many people self-medicate with comfort food during stress, which increases BMI over time

• Recognising and addressing stress-eating is key to breaking the CAR–stress–obesity cycle

Conclusion:

• Stress and obesity are closely connected, which means that they should be studied and treated together

Evaluation of cortisol, stress & obesity

Strengths

• Strong biological evidence for the link between cortisol and stress makes the obesity-related findings convincing

• Stress management strategies (e.g., walking, meditation, taking a warm bath) are accessible and practical for most people who require to a solution to their obesity

Limitations

• Tackling stress-related eating is difficult because eating is pleasurable, making behaviour change hard to sustain

• Individual differences are not accounted for, as not everyone eats more when stressed; some lose their appetite instead

  • This limits the explanation, as stress does not affect all people in the same way

Link to concepts

Measurement

• Conducting a literature review is a good way of gaining a comprehensive appreciation of a complex issue such as stress-related obesity

  • Drawing from a range of cognitive, sociocultural and biological research, it is possible to gain a holistic understanding of the issue rather than focusing on one narrow and possibly limited explanation of a health problem

Bias

• Confirmation bias is a potential threat to validity with a literature review

  • The researcher must practise reflexivity to ensure that their own biases, prejudices and preconceived ideas do not lead to them only selecting data which supports their research hypothesis/objective