Psychosocial stress and change in weight among US adults.
Am J Epidemiol. 2009 Jul 15;170(2):181-92. Epub 2009 May 22.
Block JP, He Y, Zaslavsky AM, Ding L, Ayanian JZ.
Harvard Center for Population and Development Studies, Harvard School of Public Health, Boston, Massachusetts 02115, USA.
The association of psychosocial stress with weight gain may have important implications for clinical practice and workplace and public health interventions. To determine whether multiple domains of psychosocial stress were associated with weight gain from 1995 to 2004, the authors analyzed a nationally representative longitudinal cohort of 1,355 men and women in the United States. Change in body mass index was assessed for multiple domains of psychosocial stress related to work, personal relationships, life constraints, and finances, controlling for other factors associated with weight gain. All analyses were stratified by sex and weighted to account for the complex survey design.
Among men with high baseline body mass index, weight gain was associated with increasing levels of psychosocial stress related to job-related demands (P < 0.001 for interaction with baseline body mass index), lack of skill discretion (P = 0.014), lack of decision authority (P = 0.026), and difficulty paying bills (P = 0.004).
Among women with high baseline body mass index, weight gain was associated with job-related demands (P < 0.001 for interaction with baseline body mass index), perceived constraints in life (P < 0.001), strain in relations with family (P = 0.016), and difficulty paying bills (P = 0.010). Interventions to address psychosocial stress may limit weight gain among overweight and obese men and women.
PMID: 19465744
http://www.ncbi.nlm.nih.gov/pubmed/19465744?
Discussion:
One of my clinical observations is that approximately 9 out of 10 people will gain weight under significant stress. This is true even if they do not change their diet.
I hypothesize that some of the following mental circuits are possibly involved as follows:
Environmental stress leads to an increase in norepinephrine signaling – the primary signal for stress. Increased norepinephrine signaling causes insulin resistance. Insulin resistance leads to an increase blood sugar. The increase in blood sugar leads to an increase in insulin signaling, which then allows glucose to enter cells of the body, lowering blood sugar. The increase in insulin signaling simultaneously triggers lipogenesis and blocks lipolysis in fat cells, thus enhancing fat storage, leading to obesity.
Additionally, the increase in stress/norepinephrine signaling increases ACTH signaling. This leads to an increase in adrenal cortex signal production of cortisol, progesterone, DHEA, testosterone, estrogens, androstenedioine, etc. The increase in cortisol signaling triggers hepatic gluconeogenesis, and if high enough also increases insulin resistance. This then leads to an increase in insulin signaling and enhanced fat storage, leading to obesity.
Under chronic or severe stress (particularly stresses related to social status), the increase in norepinephrine signaling leads to an increase in microglial pro-inflammatory cytokine signaling. There is also direct activation of immune system cells by direct neural connections to lymph nodes. This also increase pro-iknflammatory cytokine signaling. The increased production of pro-inflammatory cytokine signaling can trigger defensive behavioral programs in the nervous system. This may lead to hypothalamic-pituitary-adrenal axis dysregulation, which leads to impaired adrenal cortex signal production in response to stress. This leads to lower cortisol signaling and suboptimal gluconeogenesis. suboptimal gluconeogenesis leads to lower blood sugar (which can hide insulin resistance, which also compounds the problem). Lower blood sugar levels may then trigger excessive food intake, leading to obesity.
Increased stress, enhanced pro-inflammatory cytokine signaling, hypothalamic-pituitary-axis dysregulation with lower cortisol production also leads to impairment of thyroid signaling. TSH may be reduced centrally, T4 to T3 conversion may be impaired either in brain or in the body, Free T3 levels may decline or hypothyroidism at the tissue level may occur. This leads to reduced metabolic rate and eventually, obesity.
Why do some people not gain weight under stress?
Some people lose weight rather than gain weight under stress. You would think they are lucky, but they may be just as ill as those who gain weight.
Eating food triggers an increase in norepinephrine signaling, leading to increased sympathetic nervous system activity. The sympathetic and parasympathetic nervous system act as a team when it comes to digestion. The increase in norepinephrine signaling leads to an increase in cortisol signaling, which triggers gastric acid production, contributing to the digestive process. Cortisol is also an anti-inflammatory signal, which helps quell inflammatory processes involved in digestion.
The vast majority of the immune system’s cells are also located around the stomach and intestines. They are the second line of defense against our more vulnerable entry point for infection.
When stress signaling is chronically elevated, immune system activity may also be chronically elevated.
When stress/norepinephrine signaling is chronically elevated, a quandry occurs when it comes to eating – or even swallowing: eating food increases stress signaling. For some people, the increased stress of eating outweighs the benefit of food intake. This leads to the mind’s choice to avoid eating under stress.
Under stress, the elevated immune system activity in the gut also may predispose a person to irritable bowel syndrome, food allergies, and other gastric problems. This would lead to the development of behavioral programs to avoid eating under stress.
And finally, elevated pro-inflammatory cytokine signaling under stress may trigger defensive behavioral programs in the nervous system which may reduce food intake, rather than increase food intake.
Dr. M