Fat and happy
You might find it strange to find me writing about an animal study immediately after pointing out that animal studies should be taken with a grain of salt. The study under consideration in this post, however, is a little different in that all the various components of this animal study have been shown to hold constant in human studies; it’s the big picture presented that I find tremendously intriguing and probably pretty accurate.
The study, entitled “Chronic stress and comfort foods: Self-medication and abdominal obesity,” appears in the July 2005 issue of the journal Brain, Behavior, and Immunity, and is applicable to all of us.
The authors start by laying out the physiology of stress as it applies to the brain and adrenal glands. In short, in an almost oversimplified version of the stress response, i.e., what happens physiologically when we get stressed, here’s what happens.
A stressor (something causing stress; can be either physical or psychological) stimulates the hypothalamus to release a substance called corticotrophin-releasing factor (CRF), which, in turn, stimulates the pituitary gland to release adrenocoticotropic hormone (ACTH). ACTH travels to the adrenal glands and stimulates the release of cortisol, the so-called fight or flight hormone. When animals in the wild–and pre-modern humans–are (were) threatened, they either run away from the stressor or confront it. In either case the body needs a ready source of energy which is available for anaerobic use. Since fat can really only be metabolized in the presence of oxygen, or aerobically, that leaves glucose, which can enter the cells and be used under anaerobic conditions. Anaerobic conditions typically occur when one has to expend high amounts of energy over a relatively short period of time, as when running full speed away from danger or engaging in a fight. So, during those times, glucose is the fuel required.
Cortisol provides the immediate surge in blood glucose by converting protein–usually from muscle–to glucose.
The high levels of both ACTH and cortisol feed back on the hypothalamus telling it to quit pumping out CRF. If the stress remains high, however, the hypothalamus continues pumping out the CRF, which ends up producing more cortisol and, consequently, more blood sugar. As the stressful situation resolves, the feedback of ACTH and cortisol combined with this reduction in stress turns off the production of CRF, and things return to normal.
As we all know, being under stress is no fun. Part of the uncomfortable feeling we experience while stressed and immediately after is a consequence of the cortisol and all the other stress hormones–adrenalin, for example–that are surging through us. As time passes after the stressful event, these hormones normalize, and we feel better. But what happens if the stress doesn’t go away? What happens if the stress is chronic?
We have pretty much the same response to chronic stress as we do to acute stress although a little bit diminished. Cortisol and the other stress hormones remain elevated more than normal because CRF and ACTH are in stress mode. And we perceive the effects of chronic stress the same as we do acute stress, just to a somewhat lesser degree.
Here’s where the study comes in. Remember the study that launched us into this dialogue?
It turns out that rats subjected to chronic stress given the choice will begin consuming “comfort foods,” sugar and fat, will increase their caloric efficiency (will gain weight on fewer calories), and will gain fat in their abdominal area. Sound familiar? What’s more, this whole situation is augmented by elevated insulin levels. And, in the presence of insulin the increased abdominal fat sends a signal somehow (maybe through an as-of-yet undiscovered hormone or peptide?) to the hypothalamus to cut back on the release of CRF.
In other words chronic stress causes animals to eat more sugary, fatty foods and increase their abdominal fat, which then feeds back and shuts off or markedly reduces the stress response that makes them feel so uncomfortable. Makes perfect sense.
Anyone who has tried to lose weight knows that it’s always easier when things are rosy and much, much more difficult when the situation is stressful. Now we’ve at least got a reason. When things are going great, it’s easy to stick to a diet; when we get stressed, it’s comfort food here we come.
What to do about it? As the article points out:
Rather than indulging in “comfort foods” to feel better during periods of chronic stress, it behooves us to find a means to remove or reduce the chronic stressor.
I agree. But I also believe that knowing what’s going on can be a big help, which is why I find this article so important. It makes it easier for me (but then maybe not anyone else) to ward off a craving for something that’s going to sabotage me if I know why I have the craving in the first place.
We all know that stress control and cortisol reduction is good for us in in terms of our general health and well being–MD and I even wrote about it in the Protein Power LifePlan but I know that we will now certainly pay more attention to stress-reduction as an important component of weight-loss therapy.