Stress Weight Gain: Does Body Weight Gain Due to Stress Imply That Calories Don't Actually "Count"?
Stress weight gain is a remarkable phenomenon, especially when viewed through the prism of the conventional theory that calories "count." How many times have you heard the dictum that "a calorie is a calorie"? How many times have you heard that the key to weight loss is to "eat less and exercise more"? How many times have you been told that obesity results from overeating and not getting enough activity?
We believe that stress weight gain occurs because we believe that stress somehow acts on our appetite and/or on our ability to "burn off" calories. This establishes what's called a positive caloric balance, which drives us to accumulate fat in our fat tissue.
All of these ideas ultimately derive from a single interpretation of the first law of thermodynamics: the Caloric Balance Hypothesis.
The Lipophilia Hypothesis, an alternative interpretation of the first law, tells us that hormonal and physiological factors – in particular our insulin and blood sugar levels – regulate how much fat gets into our fat tissue. Our fat tissue regulates our caloric balance. So when you gain fat, your appetite increases and/or your metabolism slows. Stress weight gain occurs because being stressed somehow increases our blood insulin levels; the more insulin we secrete, the more fat we store in the fat tissue.
So we have two theories about what causes stress weight gain. And the evidence overwhelmingly appears to support the second proposition:
1. For instance, check out this article: "Four things that make you fat (not gluttony, not sloth)."
The authors nod to the Caloric Balance Hypothesis by first insisting that eating less and exercising more cause weight loss. But then the article dives into this very interesting section on stress weight gain:
"While research hasn't yet determined all the factors in the stress-weight gain feedback loop, there appears to be evidence that stress leads to weight gain -- just as putting on a few pounds can lead to stress.
One recent study found that more than 56% of stressed-out adolescents were obese, versus 47% of the less-stressed. Previous research has identified a biological switch in mice that makes the body accumulate fat. Significantly, mice that were eating a healthy diet did not put on weight, even when stressed... Another study showed that there's a biochemical trigger in the brain that prompts mice (and possibly humans, too) to seek out comfort foods when under the kind of long-term chronic stress we all experience; not only that, but the same hormone primes the body to pack on belly fat."
2. Here is another interesting article: "The relationship between stress and weight control behavior in African American women."
"Statistical analyses of the data reveal a positive correlation between body weight and stress in that women who are more overweight were experiencing more stress."
Obviously, correlation does not imply causation, but this article does a good job of establishing that an association clearly exists between stress and obesity.
3. Here is another curious article on stress weight gain: "Endoplasmic reticulum stress links obesity, insulin action, and type 2 diabetes."
"Cortisol induced insulin resistance in man: impaired suppression of glucose production and stimulation in glucose utilization due to a post receptor defective insulin action."
Cortisol is also known as the "stress hormone." We secrete it in response to stressful situations.
4. This article tells us that:
"Hypercortisolemia increased postabsorptive plasma glucose... and plasma insulin concentrations and rates of glucose production and utilization."
So stress causes hypercortisolemia, which in turn causes an increase in plasma insulin levels. This observation fits perfectly with the Lipophilia Hypothesis.
So just to review: Here's the chain of cause and effect:
a. a stressful situation occurs... b. causing an increase in cortisol levels... c. causing an increase in insulin levels... d. causing more fat to be stored in the fat tissue... e. causing a positive caloric balance.
5. And here is one more article on stress weight gain: "Effects of morning cortisol elevation on insulin secretion and glucose regulation in humans."
The authors looked at:
"the effects of an acute elevation in morning plasma cortisol on the daytime profiles of plasma glucose, serum insulin, and insulin secretion under constant glucose infusion...[They found that] an increase in plasma cortisol, even one of very small amplitude, [led to] an abrupt inhibition of insulin secretion without changing glucose concentration. Larger cortisol elevations... were additionally associated with the appearance of insulin resistance, which developed 46 hours after the cortisol elevation and persisted for greater than 16 hours."
These studies -- and surely many others -- show that changes in our cortisol levels change our insulin levels, which in turn almost assuredly change the amount of fat we store in our fat tissue. This neatly accounts for stress weight gain.
Once again, the Lipophilia Hypothesis seems to explain the evidence elegantly and the Caloric Balance Hypothesis seems to run into a brick wall.