Is HIIT (High-Intensity Interval Training) Bad for You?

The popularity of high-intensity interval training (HIIT) is on the rise. You might know HIIT is a workout that alternates between intense bursts of activity and fixed periods of less-intense activity or even complete rest. HIIT workouts can be performed on all exercise modes, including cycling, walking, swimming, elliptical cross-training, and in many group exercise classes. It is often marketed as an efficient workout to achieve weight loss.

How HIIT Works?

One of the reasons for HIIT’s popularity is the post-exercise calorie burn which makes it more efficient than traditional steady state exercise. The post-exercise period is called “EPOC”, which stands for excess postexercise oxygen consumption. This is generally about a 2-hour period after an exercise where the body is restoring itself to pre-exercise levels, and thus using more energy. The vigorous contractile nature of HIIT workouts makes the EPOC modestly greater, adding about 5-15% more calories to the overall workout energy expenditure.

Besides its efficiency, studies have shown HIIT results in an increase in metabolism, improved cardiovascular fitness and improved muscle tone along with weight loss. It can be done anywhere, without equipment and in a group, and can be seriously challenging.

With so many benefits, I understand the popularity of HIIT and more people including it in their exercise regimen. However, is it always beneficial for everyone to indulge in HIIT or are there cases when it can do more harm than good?

When to Avoid HIIT

I have seen people who exercise regularly feeling run down, losing muscle mass, gaining fat, and under constant exhaustion; something completely contrary to their fitness goals. People often ask me, “I train hard to achieve my fitness goals, how am I not making progress?”.

First, everyone is different and responds to exercise differently. People with rather sedentary lifestyles or periods of physical inactivity may have an increased coronary disease risk to high-intensity exercise. Family history, cigarette smoking, hypertension, diabetes (or pre-diabetes), abnormal cholesterol levels and obesity will increase this risk.

Stress and lack of sleep

Likewise, for those who suffer from high stress or adrenal fatigue, HIIT could cause serious harm to health. Intense exercise may place additional stress on adrenal functions. Cortisol is released by the adrenal glands under conditions of high mental and physical stress and is the body’s primary catabolic hormone. HIIT may stimulate significantly acute cortisol response and chronically high level of this hormone can increase the risk of a number of health issues including weight gain, depression, digestive issues, chronic fatigue, sleep problems and brain fog. Studies have found that excess cortisol can stimulate fat gain and cause poor quality sleep.

Both too much and too little cortisol can affect thyroid function. Elevated levels of cortisol can suppress the release of active thyroid hormone in a variety of ways. For example, high cortisol may suppress the release of thyroid stimulating hormone in HPA axis or cortisol is required for the conversion of T4 to T3 (active thyroid ) and in adrenal fatigue cortisol is depleted. This may lead to conditions such as hypothyroidism.This can cause depression, weight gain, and digestive dysfunction along with a variety of other symptoms. In other words, a person might end up gaining weight; which is counterintuitive and opposite of the desired objective of training.

Some of the symptoms of hypothyroidism are fatigue, lack of energy, sluggishness in the morning, poor concentration and memory, muscle pain, weakness or cramps, low sex drive, high cholesterol and even low-grade depression.

People often combine high-intensity exercise with low carb diets; this is an additional factor in cortisol rise. Blood sugar level drops with low carb meals and the body needs cortisol to take glucose from muscles and liver. This results in a rise in cortisol, which can, in turn result in poor sleep and stimulate fat storage enzymes.

Should you quit HIIT or high-intensity training?

Done correctly, HIIT provides numerous health benefits for a number of people. However, to maximize its benefits, it needs to be done the right way and in moderation. Compounding an already high-stress work or general life stress with the excess stress from exercise can actually make a person sick.

Adequate recovery from HIIT is vital in balancing hormones and avoiding adrenal burnout. Limit your high-intensity exercise to 2 times per week and even avoid it if you are suffering from health issues like adrenal stress or autoimmune disease. Make sure to get adequate sleep to recover from intense training. If you have trouble sleeping, try reducing the intensity of your exercise as it might be a symptom of overtraining.


Include relaxation techniques such as a sauna, meditation and yoga in your exercise schedule. These and other techniques to relax and combat stress can help you recover more quickly and reduce cortisol levels, helping you reach your health and weight loss goals faster.

Drink adequate amounts of water during and after the exercise and eat clean, unprocessed food. Consider supplementation with B-complex, Vitamin C and magnesium to support adrenal function and aid recovery. I also suggest eating more carbohydrates, which might seem counterintuitive to all the popular advice for reducing fat and improving body composition. A combination of high-intensity training, other stressors and low carb diets can raise cortisol levels and create weight loss resistance.

So, what does it all mean?

The bottom line is that there is no one-size-fits-all approach to exercise and same applies to HIIT. If you make this a part of your exercise regimen, ensure adequate rest and nutrition. Always use your best judgment and listen to your body. Avoid it and consider professional help if you have any of the symptoms mentioned above.

If you exercise regularly, I would like to hear your experiences with various kind of exercise. Do you feel that a particular kind of exercise affected your health negatively or did not have the desired impact? You can comment below or on my Facebook page.


PS: Do you want to understand the underlying cause of your weight gain and follow a step by step program to lose weight and feel amazing? Contact us below.

Dr Menka Gupta


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