This is part 1 of how stress affects weight. Part 2 offers ideas for counteracting the effects of stress.

Have you ever noticed that during stressful times, even if your calories haven’t crept up or your workouts decreased, that you’re just not as toned?

By contrast, during times when you are at ease, having a good time, and largely free of stress, that even without (consciously) changing your diet or increasing your exercise, the weight just fell off easier?

I certainly have found this to be true. When I’m truly not stressed, my muscle definition is more apparent and the scale tends lower.

Various studies have confirmed the impact of stress on body composition, demonstrating that stress and the resulting cortisol secretions leads to weight gain and increased mass around the the middle [AHA].

Each person responds to stress differently, and research suggests some people tend to eat less (or not at all) during stressful periods. This group may not have the same weight gain most of us experience, but they can still lose muscle tone because of nutritional deficits or because of the actions of cortisol.

How Stress Affects Weight

Stress_BWThere are a multitude of factors stemming from stress that decrease muscle tone and increase weight and flab; among these are eating habits, changes in digestion, poor quality sleep, and the effects of cortisol, the ‘stress’ hormone.

Eating Habits 

In many people, increased cortisol and adrenal secretions also leads to “stress eating” [Obesity Reviews journal]. Why do we eat more when stressed? Because for many of us food is distraction, comfort, safety, relaxation, and happiness. Biochemically, food provides a boost to neurotransmitters like serotonin and dopamine, which make us feel good. Thus, to counteract the effects of stress, we tend to eat more in an attempt to feel better. Stress eating is perhaps the single biggest contributor to weight gain during stressful times.


Stress also negatively impacts sleep. Cortisol is the ‘wake up’ hormone so when it’s not fully dialed down at the end of the day, it can be difficult to truly relax, turn off the brain, and alleviate muscle tension thus inhibiting deep, restful sleep. In the absence of sufficient quality sleep, our bodies don’t properly rest and repair, reduce inflammation, clear the digestive system or the liver, and perhaps most importantly, don’t reset the stress and cortisol baselines. Furthermore, sleep deprived people tend to eat more to boost their energy, and thus be susceptible to increased calorie consumption and weight gain (Learn more about the importance of sleep.


The fight or flight response (the activation of the parasympathetic nervous system) causes blood to flow away from the digestive system and the muscles to tense. Eating under these circumstances means the body won’t produce enough HCL, digestive enzymes, and peristaltic movement to facilitate complete digestion. The stomach area may feel contracted, knotted, or heavy, and digestion just doesn’t proceed. The buildup of undigested food, though it may not necessarily contribute to weight gain, can cause increased inflammation and water retention, and strain the liver. The bloated, heavy feeling may be perceived as weight gain or increased roundness of the middle. (Read more about the impact of anxiety, worry, and stress on digestion.)

Fat Accumulation

The stress of today is very different than that which our ancestors experienced thousands of years ago. To them, stress meant famine, drought, attack, or other life-threatening danger. To ensure the body has adequate energy stores and resources to survive a famine or fight off an attack, cortisol works very efficiently to store fat (i.e. save calories for later). It’s preferred storage location is around the organs in the torso, keeping those calories close at hand and protecting the organs from intrusion and damage.

This worked well for our ancestors when food was much harder to come by and stress was much less frequent. However, with an oversupply of calories and stress, many of us have too much belly fat. The storage of calories as fat is also prioritized over the (re)building of muscle because it is a quicker source of energy, which is another way that stress reduces muscle definition. Stress has contributed widening waistlines and rising weight. (Read more about how stress drives carb cravings, which compounds weight gain around the middle.)

Because stress so easily drives up weight and stress is so pervasive, in order to manage or lose weight, we must learn to better cope with and reduce the effects of stress. That topic will be covered in the post next week.

This is part 1 of how stress affects weight. Part 2 offers some tips to manage stress and ideas how to maintain weight and muscle definition during stressful times.