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Exercise, Hormones & Weight Loss: Q&A with Sara Gottfried, MD

A personalized lifestyle medicine approach to exercise prescriptions

by Sara Gottfried, MD

Exercise is key to overall health, but sometimes the wrong approach can do more harm than good. It’s likely one of the reasons you’ve encountered patients who are struggling to achieve results despite every effort to lose weight and improve their health. Thankfully, there’s more to the story. We sat down with Sara Gottfried, MD to discuss the connection between exercise, hormones, and healthy weight loss.

Sometimes exercising too much can make it more difficult for people to lose weight. How have you seen this with your own patients?

As you know, working out is vital to a healthy, happy body and mind. However, when it comes to physical activity, it’s possible to have too much of a good thing. In fact, spending countless hours at the gym may be counterproductive to hormone function, particularly the hormones that are involved in the body’s metabolism and how it burns and stores fat. If a patient works out excessively, particularly when not completely recovered or warmed up, he/she increases the risk of injury and overdrive, a state of overactivated and unbalanced stress load. Over time, overdrive commonly leads to dysfunction of the control system for hormones—i.e., the hypothalamic-pituitary-adrenal-thyroid-gonadal (HPATG) axis.

Even if your patients are training for a specific event or sport, racking up countless hours on the road or treadmill will likely trigger an undesired hormonal response, which can negatively impact their attempts to lose weight.1

Which hormones prevent weight loss and how?

Cortisol, a major player in body fat storage, increases in response to an elevation in stress (both emotional and physical). The longer the workout, even at moderate intensity, the more cortisol one’s body is releasing.2 For some people, chronic cardio raises cortisol too high and leads to an overactive stress response system. Anything that raises cortisol levels and keeps them elevated will make it very difficult to lose weight.

Additionally, there may be a counterproductive relationship between exercise and the hormone ghrelin in some cases. For example, high-intensity interval training (HIIT) transiently raises ghrelin in mice.3 And although exercise typically suppresses ghrelin, a randomized trial found that exercise increased ghrelin in dieting women,4 so women may be at a disadvantage when it comes to dieting and exercise. As you know, stress can also raise ghrelin levels.5 Combining elevated stress with vigorous exercise may leave patients feeling hungrier for calorie-dense comfort foods and make it harder for them to quit snacking after dinnertime.

Bottom line: Too much ghrelin is a barrier to weight loss because it increases appetite and subsequent food intake.5 The more ghrelin in your system, the hungrier you are and the more likely you are to have problematic overeating,6 particularly for women who are combining diet with exercise. As such, we want to help patients lower their ghrelin levels in order to lower body weight set point.

What type of patients tend to overexercise in this manner?

In my latest book, Brain Body Diet, I discuss the case of one of my patients, who represents the type of person who overexercises. This patient “idles high.” She is stuck in hyperarousal, the specific physiological condition prior to addiction. It’s a state of heightened physical and emotional tension marked by anxiety, stress, exaggerated startle response, insomnia, fatigue, and accentuated personality traits. She also has what I call a “spread addiction,” addictive behaviors spread across multiple stimuli—exercise being one of them. Some may also define it as a Type A personality: ambitious, competitive, driven, and impatient. It can be difficult to lose weight in this way.

The other groups of people who overexercise include the following:

  • Women who are trying to lose weight, but are going about it all wrong. As you know, fat loss in women is different than fat loss in men—but that’s a topic for another time!
  • Men or women who have trouble assessing the need for recovery. For these people, I recommend measuring heart rate variability (described below). 

How can you tell if patients’ extreme exercise habits are preventing weight loss?

If patients are not able to lose weight despite their exercise regimens, it is recommended to measure their hormones. Start first with cortisol. You can run a blood serum test or try the DUTCH test (Dried Urine Test for Comprehensive Hormones), which I find particularly effective. If your patient’s results indicate a hormonal imbalance, this could be the reason why your patient is not losing weight despite extreme exercising.

What do you advise patients to do in these cases and why?

I recommend that patients measure their heart rate variability (HRV) daily to determine what kind of exercise is recommended for them on any given day. HRV is the pattern of one’s heart rate. If a patient has a resting heart rate of 60, they might assume that’s an acceptable one beat per second. However, this is a very low HRV. We actually want variability between the time of each heartbeat, and it’s important that we explain this to our patients. For example, if the first gap between heartbeats is 1.00 seconds, and the second is 1.02 seconds, and the next 1.05 seconds, and so on, this would indicate good HRV.

Moreover, the more a person’s heart beats irregularly, the healthier he/she is.7 Research proves that when our HRV is high or optimized, our bodies are demonstrating better stress resilience and health. A low HRV (little variation between beats) actually indicates less resilience and greater stress—so an intense workout may not be a good idea for any patient as it will only add to their stress levels and further prevent healthy weight loss.

Another recommendation is to buffer cortisol with vitamin C. High levels of vitamin C have been shown to lower postrace blood cortisol levels in ultramarathon runners.8

What do you believe is the most successful approach to exercise?

I believe the one-size-fits-all approach is not helpful for most things, including exercise. Ideally, an exercise plan should be individualized. That’s why measuring your patients’ hormone levels and heart rate variability is a good way to form a foundation for a personalized exercise plan that benefits the body, promotes weight loss, and does not cause undue negative effects. For example, on the days when HRV is low, I would recommend that patients forgo an intense cardio workout and take a yoga class instead.

To burn fat and lose weight, strength training is also important. Additionally, more and more research is telling us that burst exercise is better for our health and fitness than longer periods of sustained exercise.9 Burst exercise, as you may know, means short duration done at a high intensity with variability. Chronic or sustained exercise, on the other hand, means continuous movement with less intensity and little variability—for example, a long run at a steady pace. Burst exercise is highly beneficial as it improves blood pressure, insulin sensitivity, cholesterol profiles, and cardiovascular health and also decreases abdominal fat and body weight (while maintaining muscle mass).10,11

While exercise is essential for managing weight and improving health, it can also have a negative effect. Some exercise (like running) places so much stress on the body that cortisol shoots sky-high. In general, I would advise that patients not exercise in an obsessive desire to burn calories and lose weight. Instead, encourage them to practice yoga, meditation, or guided visualization several times a week and incorporate more adaptive burst training into their routines.

To learn more about helping your patients stay healthy through the application of personalized lifestyle medicine, stay tuned for more Q&A sessions with Dr. Sara Gottfried.


  1. Lac G et al. Changes in cortisol and testosterone levels and T/C ratio during an endurance competition and recovery. J Sports Med Phys Fitness. 2000;40(2):139.
  2. Rojas Vega S et al. Acute BDNF and cortisol response to low intensity exercise and following ramp incremental exercise to exhaustion in humans. Brain Res. 2006;1121(2):59-65.
  3. Mani BK et al. Ghrelin mediates exercise endurance and the feeding response post-exercise. Mol Metab. 2018;9:114-130.
  4. Mason C et al. The effects of separate and combined dietary weight loss and exercise on fasting ghrelin concentrations in overweight and obese women: a randomized controlled trial. Clin Endocrinol (Oxf). 2015;82(3):369-376.
  5. Buss J et al. Associations of ghrelin with eating behaviors, stress, metabolic factors, and telomere length among overweight and obese women: preliminary evidence of attenuated ghrelin effects in obesity? Appetite. 2014;76:84-94.
  6. Dickson SL et al. The role of the central ghrelin system in reward from food and chemical drugs. Mol Cell Endocrinol. 2011;340(1):80-87.
  7. Sandercock GRH et al. Changes in short-term measures of heart rate variability after eight weeks of cardiac rehabilitation. Clin Auton Res. 2007;17(1):39-45.
  8. Peters EM et al. Vitamin C supplementation attenuates the increases in circulating cortisol, adrenaline and anti-inflammatory polypeptides following ultramarathon running. Int J Sports Med. 2001;22(7):537-543.
  9. Shiraev T et al. Evidence based exercise – clinical benefits of high intensity interval training. Aust Fam Physician. 2012;41(12):960-962.
  10. The American College of Sports Medicine. High-Intensity Interval Training.,.3.aspx. Accessed January 14, 2019.
  11. Mayo Clinic. Rev Up Your Workout With Interval Training. Accessed January 14, 2019.


Sara Gottfried, MD is a board-certified gynecologist and physician scientist. She graduated from Harvard Medical School and the Massachusetts Institute of Technology and completed residency at the University of California at San Francisco. Over the past two decades, Dr. Gottfried has seen more than 25,000 patients and specializes in identifying the underlying cause of her patients’ conditions to achieve true and lasting health transformations, not just symptom management.

Dr. Gottfried is a global keynote speaker who practices evidence-based integrative, precision, and Functional Medicine. She recently published a new book, Brain Body Diet and has also authored three New York Times bestselling books: The Hormone Cure, The Hormone Reset Diet, and Younger.


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