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Common Exercise Myths by Annie Rubin, MSN, RDN

When I counsel my clients on their nutrition and eating patterns, the topic of exercise always comes up. Adding movement to your daily routine can do wonders for your physical and mental health. However, there are many misconceptions about exercise and its benefits. Here are the top exercise myths that I discuss with my clients.

Myth One: You need to exercise to lose weight

Many clients tell me they are unable to lose weight because they don’t exercise. But, in fact, exercise plays a very small role in weight loss. In studies that examined weight loss from either diet or exercise, only 20% of weight loss could be attributed to exercise.

Your metabolic rate determines how many calories your body burns in a given day. It comprises three components: your resting metabolic rate, physical activity and energy for food digestion and absorption. Your resting metabolic rate—the one you have very little control over—makes up most of your metabolic rate. How active you are accounts for just 15–30% of your metabolism.

In addition, exercise does not burn many calories. On average, a moderate 30-minute workout burns around 120 to 400 calories, depending on the type of exercise and your body weight (more in this article). That calorie burn equates to one large banana or a plain bagel with cream cheese. The other side effect of exercise is that it makes us hungrier because of our body’s need to refuel and replace the energy that was lost. Focusing on what you eat can lead to the biggest weight loss gains.

Myth Two: Weight training will make you bulky

Women generally shy away from strength training because they believe that lifting weights will make them look bulky. While it is not impossible to get a bodybuilding physique, it takes a lot more time and energy than the average person spends in the gym to reach that potential. Another reason why women will not bulk up can be attributed to our hormones. Women have less circulating testosterone than men, and testosterone is directly related to muscle mass and strength. Therefore, one of the best benefits of weight training is building that lean muscle mass as it is a good way to raise your resting metabolic rate.

Myth Three: There’s no such thing as too much exercise

While movement has its benefits, too much exercise can be harmful. While low to moderate amounts of exercise can help reduce inflammation and reduce oxidative stress, too much exercise can have the opposite effect. This is known as the J-curve of exercise, which compares the intensity of movement to adverse health risks. Being completely sedentary clearly puts your health at risk. As the amount of exercise increases, the benefits to your health increase. However, there is an inflection point where increasing exercise intensity starts to become less beneficial for you. Too much exercise can:

  1. Suppress your immune system. Several studies on runners have shown that exercising more 1.5 hours can impair the body’s ability to fight infections. In fact, marathon runners are two to six times more likely to develop upper respiratory tract infections than non-marathon runners (see more here).

  2. Increase your stress hormones. Prolonged exercise or training at high intensities over a long period may cause your body to over-produce epinephrine and cortisol. When these hormones remain elevated, your body stays in a stressful state, affecting the sympathetic nervous system and increasing inflammation.

  3. Affect your gut. Runner’s diarrhea is real. This is because intense exercise redirects the blood flowing to your intestines to other areas of your body that need support (such as muscles and tissues). When this happens, the intestinal cells are basically starved of the nutrients they need to function. Additionally, exercise at or above two hours at a 60% VO2max may increase intestinal permeability, allowing potentially harmful agents to sneak into your circulation.

Myth Four: Doing sit-ups will help you lose weight in your mid-section

While having a strong core is important, performing abdominal exercises for the sole purpose of shrinking your belly is not an effective way to exercise. Fat may be broken down during exercise and used as energy, but those fat cells can come from anywhere in the body, regardless of the area being exercised. Several studies have shown that spot reduction does not work. Instead, it is more effective to combine strength and cardiovascular movement to both tone up areas and lose body fat.

Myth Five: If the scale isn’t going down, I must not be exercising enough

The number on the scale is just a number; it is not a reflection of your health. This concept is essential for anyone who is trying to improve their health by incorporating exercise. Exercise builds muscle, and muscle weighs more than fat. So, if you are working out and eating healthy, it is quite possible that your progress will not be reflected on the scale. Instead, try using other metrics to track progress, such as body measurements, labs and how your clothes fit.

Fact: Exercise has MANY benefits that can help improve your health and wellbeing There are very few downsides to including moderate exercise in your daily routine. Some of the very important benefits of movement include:

  • Strength exercises help boost your metabolism by building up lean muscle mass.

  • Exercise can improve your blood sugar. This is because physical activity helps the cells absorb sugar from the bloodstream to lower your blood glucose more efficiently. In other words, exercise can help improve insulin sensitivity.

  • Physical activity can boost your mood.

  • Regular exercise can help you sleep better. One study found that 150 minutes of moderate to vigorous exercise per week for six months improved sleep quality for women diagnosed with insomnia.

  • Exercise that uses either your own body weight (running, walking, dancing) or weights can help strengthen your bones and improve bone density.

Moving your body can have a positive and powerful impact on your overall health. Just remember to:

  • Combine healthy eating habits with exercise to make a bigger impact on your wellness goals.

  • Focus on moderate exercise most of the time.

  • Incorporate resistance training to support lean muscle tissue and boost your metabolism.

  • Vary your exercises to build strength and cardiovascular health.

Avoid using a scale to track your progress.


Annie Rubin, MSN, RDN

Annie Rubin is a registered dietitian and holds a Master’s degree in Nutritional Science. She completed her dietetic internship at Stanford Health Care. Before starting her private practice, Annie worked at Stanford as an outpatient dietitian in the Bariatric and Metabolic Interdisciplinary (BMI) clinic for surgical and non-surgical weight loss patients. She is currently the dietitian at The Wellness Studio at The Village Doctor. Annie is also an adjunct professor at San Jose State University in the Nutrition, Food Science, and Packaging Department. In her spare time, Annie loves to run, hike and spend time with her family.


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