Although the effects of stress on metabolism vary from person to person, it is estimated that up to a 7% reduction in the resting metabolic rate is seen with stress-induced weight loss. (5)
But, what exactly is this 7% that has been so dramatically reported on?
What does it take to trigger a drastic weight loss?
The body has a response to physical stress that lasts for anywhere between 24 and 72 hours. (15, 26, 29) However, it is estimated that a 6.5% reduction in resting metabolic rate will occur during the initial phases of stress (26) .
There are two possible reasons why a significant weight loss can occur. One of them is that the body has a mechanism designed to counteract the effects of the stress response. This mechanism, when triggered, is considered to be an important driver of weight loss by reducing metabolic rate to an estimated 6.5 to 7% (31, 32) .
The second reason for significant weight loss with physical stress is that the body can metabolize more calories due to increased energy expenditure and increased metabolic rate. This in turn is due to the body’s ability to store fat at a far faster rate. (23, 32, 33)
What are the biological benefits of stress reduction?
Several studies have shown that physical stress has many beneficial consequences to the metabolic system. A recent review found that physical stress reduces serum triglycerides by as much as 25% (1) .
One study found that cortisol levels dropped by as much as 40% in the two minutes following physical exertion (33) and that cortisol levels decrease immediately after exercise for 2 hours after exercise in healthy volunteers (34)
In another experiment people were given a choice between two diets and one was compared to a control diet while another was compared to a control diet with no exercise. On both of the diets, energy expenditure was increased as well as body weight increased.
But, what is a “high-fat” diet and what does it mean for metabolism?
It is clear that high-fat (high-sugar) diets are highly problematic for weight loss since there is no evidence that low-fat diets work for weight loss. So, the question then becomes why is it desirable to avoid foods like white bread, cereal or pasta? One of the primary reasons is that they contain high amounts of energy-dense carbohydrates and sugars.
Another major problem with high-fat diets is high levels