Chronic stress, the underbelly of modern life (pun intended), is perhaps as much to blame for the increased rates of obesity, cardiovascular disease, and diabetes as are other lifestyle variables such as diet and exercise. Our physiological responses to stressors were meant to be acute, short-term adaptations that allowed us to survive an immediate threat. The chronicity of modern stress has turned a very basic survival mechanism into a death trap and I’m not sure we’ve fully evolved to adapt to this new, never-ending state of stress.
Think about what happens to the body when it is faced with a stressor; it mounts a physiological response against the stressor. It doesn’t necessarily matter what the stressor is, the physiological responses are quite similar. Have you ever noticed that the early stages of illness look a lot alike, GI disturbances, heart rate changes, loss of appetite, sometimes fever, aches and pains- that general feeling that you are coming down with something? This is your body reacting to an internal stressor, an illness.
Perhaps more familiar is the stress response associated with a perceived and acute external threat, such as burglar or an impending car accident. Here, the body mounts a rapid response aimed at preparing us to fight or flee. With this type of threat, we get the adrenaline rush, the changes in brain chemistry, and the flood of cortisol that prepares us to act. It is a biochemical all-hands-on-deck. During the initial phases of stress, energy is shuttled to the muscles, cardiovascular and pulmonary tone increase, while anabolic activity (muscle building) digestion, growth, reproduction and the immune system are all suppressed. For a time, cognition is sharper. (Interestingly, this may only be true in males. In female rodents at least, stress decreases cognitive ability, quite significantly and estradiol mediates this effect.) If the stressor is not removed, the physiological stress response continues and therein lays the problem.
With chronic stress, energy stores are depleted and the muscles shift to a catabolic state (breaking down of muscle). Increased cardiovascular tone that was necessary to survive an acute stressor turns into stress-induced hypertension. The poor digestion leads to ulcers and lack of nutrient absorption. The inflammatory response goes into overdrive, the reproductive hormones and system go awry and infertility emerges (this is why many women get pregnant soon after they stop trying). When all of these stress changes are combined with a continuously suppressed immune system, illness emerges.
Chronic stress is bad, but does it make us fat? If digestion is suppressed, all of us modern women should be skinny, right? If only…
From a physiological standpoint, chronically increased cortisol levels or disruptions to the normal diurnal rhythm of cortisol release (frequent with chronic stress and depression) changes our metabolic patterns by inducing insulin resistance. Chronic stress may even make us hungrier (potato chips and ice cream anyone?) by making us leptin resistant. Leptin and its counterpart ghrelin regulate hunger and satiety. Leptin normally suppresses hunger, while ghrelin increases hunger, but with chronic stress and as weight increases, leptin’s ability to suppress hunger diminishes. Since leptin is synthesized in fat, more fat equals more leptin and often less ghrelin. As stress and weight continue to climb, the system becomes more and more dysregulated; more stress, poor digestion, poor nutrient absorption, more insulin, more carb cravings, more fat, more leptin, more fat, more stress, a disrupted menstrual cycle, high blood pressure, Type 2 Diabetes, and on and on.
When physicians suggest stress may be at the root of many health issues and prescribe that we de-stress our lives to improve our health, perhaps we ought to listen.