There’s no question that regular exercise is essential to health. Our paleolithic ancestors had a different word for exercise: life. For the vast majority of our evolutionary history, humans had to exert ourselves – often quite strenuously – to get food. We naturally spent a lot of time outdoors in the sun, walking, hunting, gathering, and performing various other physically-oriented tasks. We had no concept of this as “exercise” or “working out”. It was just life.
Things are different today. 60% of American adults are not regularly active, and 25% are complete couch potatoes – they get no exercise at all, other than walking back and forth between the car, the cubicle and the refrigerator. This lack of physical activity has profound consequences. Regular movement protects us from disease in several ways, but most importantly it prevents oxidative damage and inflammation – the primary mechanisms underlying most modern, degenerative diseases. This explains why those who are completely sedentary have between 1.5 and 2.5 times the risk of developing heart disease and a higher risk for virtually all modern, degenerative disease.
On the other hand, we’ve got the exercise fanatics. Many Americans have been caught up in the fitness craze over the last 40 years, devoting countless hours to jogging, the Stairmaster or the treadmill in the hopes of slimming down, getting healthy and preventing disease. But while this type of activity may help with stress management, research suggests that it’s useless for weight loss and may in fact be detrimental to health.
Why “cardio” doesn’t work for weight loss
When I say “cardio”, I’m referring to steady-state, repetitive activity done at a moderate intensity like jogging outdoors, running on a treadmill or climbing the Stairmaster. [Side note: the idea that you have to perform this type of activity to benefit your heart and vascular system is false. Anything that places a demand on the muscles – including so-called anaerobic activities like weightlifting – will also condition the heart and vascular system.]
Most people are surprised to learn that cardio doesn’t work for weight loss. How could this be? There are three main reasons:
- caloric burn during exercise is generally small;
- people who exercise more also tend to eat more (which negates the weight regulating effect of exercise); and,
- increasing specific periods of exercise may cause people to become more sedentary otherwise.
In an example of the first reason, a study following women over a one-year period found that in order to lose one kilogram (2.2 pounds) of fat, they had to exercise for an average of 77 hours. That’s a lot of time on the treadmill just to lose 2 pounds!
In an example of the second reason, a study found that people who exercise tend to eat more afterwards, and that they tend to crave high-calorie foods. The title of this study says it all: “Acute compensatory eating following exercise is associated with implicit hedonic wanting for food.” I love it when researchers have a sense of humor.
In an example of the third reason, one study assigned 34 overweight and obese women to an exercise program for 8 weeks. Fat loss at the end of the study was an average of 0.0kg. Not very impressive. But the researchers noticed that some women did lose weight, while others actually gained. What was the difference? In the women that didn’t lose weight, the increase in specific periods of exercise corresponded with a decrease in overall energy expenditure. Translation: they were more likely to be couch potatoes when they weren’t exercising, which negated the calorie-burning effect of their workouts.
If you’re still not convinced, the Cochrane group did a review of 43 individual studies on exercise for weight loss. Study length ranged from 3 to 12 months, and exercise sessions lasted on average 45 minutes with a frequency of 3-5 times per week. The results? On average, the additional weight loss from exercise averaged about 1 kg (2.2 pounds). Meh. Assuming they worked out for 45 minutes 4x/wk over 6 months, that means they had to exercise 69 hours to lose that 1 kg.
Why cardio may be harmful
Too much cardio exercise has a number of harmful effects on the body:
- increases oxidative damage
- increases inflammation (the root of all disease)
- depresses the immune system
- decreases fat metabolism
- disrupts cortisol levels
- causes neurodegeneration
Overtraining is especially damaging because of its effects on cortisol. We discussed cortisol at length in Step 6: Manage Your Stress, but in this context what’s important to understand is that too much exercise can disrupt our natural cortisol rhythm and drive levels too high initially, and depress them over time. Cortisol dysregulation promotes abdominal fat gain and muscle loss, which in turn causes further weight gain.
There’s also some evidence that frequent endurance exercise may promote – rather than prevent – heart disease. Dr. Kurt Harris summarized a study performed on 102 active marathon runners and 102 age-matched controls to determine the effect of aerobic exercise on cardiovascular health.
The marathoners were between 50 and 72 years of age, and they ran an average of 35 miles per week. They had no known history of heart disease or diabetes. The control group was similarly aged and also had no history of cardiovascular or metabolic disease.
You might be surprised to learn that the marathon runners were three times more likely to have heart damage than the non-runners. Among the runners, there were12 heart attacks vs. 4 attacks in the non-runners.
In another study by the same authors, the more marathoners ran, the higher their likelihood of heart disease. In fact, the number of marathons ran was an independent predictor of the likelihood of irreversible damage to the heart tissue.
Sitting – The new smoking
We’ve become a nation of sitters. Fewer than 2 percent of jobs require manual labor. We spend endless hours working at computers, watching TV, playing video games, or commuting. The typical US adult is now sedentary for 60 percent of his or her waking hours, and sits for an average of six hours (and often much more, in the case of those who work desk jobs and/or with computers). A sedentary office worker expends only ten calories per pound each day, down from the hunter-gatherer’s average of 43 to 55 calories per pound per day.
But we weren’t born to sit all day. We’re genetically designed to be physically active. The dramatic increase in sitting has had a profound, negative effect on almost every aspect of human health, from the cardiovascular and pulmonary systems to the immune system. Here are just a few specific ways that sitting harms us:
- It wrecks our metabolic function.
- It decreases the activity of enzymes that help us to burn fat, and protect us from cardiovascular disease.
- It reduces the action of insulin.
- It weakens the bones.
Most disturbingly, sitting too much shortens our lifespans. In an Australian study that followed participants over six-and-a-half years, researchers found that high levels of TV time were significantly associated with increased risk of death from heart disease as well as all other causes. Each hour of TV was associated with an 11 percent increase in death from all causes. By contrast, those who watched less than two hours of TV a day had a 46 percent lower risk of death from all causes when compared to those who watched more than four hours. These associations were independent of exercise and traditional risk factors such as smoking, blood pressure, cholesterol levels, waist circumference, and diet.
This is why some health experts have claimed that “sitting is the new smoking.” Sitting a lot shortens our lifespans to a degree that is similar to smoking cigarettes. It’s a major public health challenge that, up until recently, few were aware of.
Exercise isn’t the answer: The “active couch potato” problem
You might be thinking something along the lines of, Okay, I sit a lot—but I also work out a lot, so I’m good.
Here’s the shocker: too much sitting and sedentary time is harmful even if you’re getting enough exercise. This means you could be meeting the recommended government guidelines for exercise (that is, thirty minutes of moderate to vigorous activity five days a week) but still be at high risk of heart disease if you sit for long periods each day. A large study involving over one hundred thousand U.S. adults found that those who sat for more than six hours a day had up to a 40 percent greater risk of death over the next fifteen years than those who sat for less than three hours a day regardless of whether the participants exercised.
This doesn’t mean exercise isn’t helpful, or necessary. It is. It just means that exercise alone isn’t enough to offset the harmful effects of too much sitting.
So what is the solution?
It can be broken down into three parts:
- Less sitting (and more standing)
- More walking and “non-exercise physical activity”
- Regular periods of more intense physical activity (i.e. “exercise”)
Less sitting (and more standing)
The simplest way to sit less is to stand more. Standing engages postural muscles that increase fat burning activity, among other benefits. Standing and walking slowly increases energy expenditure by two and a half times; employees who stand while they work burn up to 75 percent more calories per day than people in sedentary jobs.
I recommend a goal of standing for about half of the day, and taking a standing break every forty to fifty minutes during prolonged periods of sitting.
Here are a few ways to reduce your sitting time:
- Get a standing desk. This isn’t always possible, depending on your work environment, but many employers are now allowing it.
- Take standing breaks. Stand for at least two minutes every forty to fifty minutes. Take a brief walk or do some light stretching. Even short breaks like this make a big difference.
- Stand up at long meetings. If you’re worried about what people will think, just tell them you have a bad back!
More walking and “non-exercise physical activity”
Non-exercise physical activity refers to all forms of physical activity other than distinct periods of exercise. This includes activities like gardening, performing household chores, walking, commuting by bicycle to work, etc.
You might be surprised to learn that even a relatively low to moderate level of physical activity will lower your post-meal blood sugar, insulin levels, and triglycerides, as well as reduce your waist circumference. You don’t have to join a CrossFit gym or do crazy amounts of physical activity in order to improve your fitness and health. Sometimes it’s the smaller changes that are the most important. Besides, it’s easier (and cheaper) to chriskresser.com 29 integrate a low-intensity activity into your daily life than an intensive, formal workout (like that expensive class at the gym you have to drive to).
Again, I’m not suggesting that exercise isn’t important. But I am saying that if you sit for most of the day and week, and think that going to the gym three or four times a week for an hour is enough, you’re mistaken. You have to increase your “non-exercise physical activity” in order to really protect yourself against the harmful effects of too much sitting.
Here are some ideas for how to do that:
- Take walking meetings.
- Use the stairs whenever possible.
- Walk or bicycle to work. (If you live too far away to walk or ride exclusively, consider driving or taking public transport part of the way, and walking or cycling for the remainder.)
- Do your own chores.
- Get a dog.
As a general goal, I suggest that most people aim for 10,000 steps a day. You can measure your steps with an activity tracker like the FitBit or Jawbone.
Regular periods of more intense physical activity (i.e. “exercise”)
In addition to standing more and doing more non-exercise physical activity, you should also incorporate regular periods of more vigorous activity (aka “exercise”).
Your goal should be:
- 150 minutes of moderate-intensity activity per week (like jogging, yoga, or dancing); or,
- 75 minutes of vigorous-intensity activity per week (like running, Zumba, or playing sports); or,
- 30 sets of highest-intensity activity per week (like sprinting, jumping rope, or resistance training); or,
- Some combination of the above
Moderate, vigorous, and highest-intensity activity are defined as follows:
- Moderate: 50 to 70 percent of maximum effort
- Vigorous: 70 to 90 percent of maximum effort
- Highest-intensity: greater than 90 percent of maximum effort
You can do this higher intensity activity in designated workouts or simply integrate it into your daily routine. For example, if you work at home, you can pepper in vigorous or highest intensity activities throughout your day, such as push-ups, pull-ups, jumping rope, etc.
The most effective training: HIIT
In contrast to cardio, this type of exercise involves performing movements at very high intensity for short periods of time – usually between 30 seconds and 2 minutes. This is sometimes referred to as high intensity interval training (HIIT).
Several studies have been done comparing HIIT to low-intensity, steady-state (“chronic cardio”, as Mark Sisson calls it) exercise, and HIIT has been shown to be superior in nearly every meaningful marker.
A pair of studies done at McMaster University found that “6-minutes of pure, hard exercise once a week could be just as effective as an hour of daily moderate activity“, according to the June 6, 2005 CNN article reporting on the study.
The study itself was published in the Journal of Applied Physiology, and it revealed that HIIT resulted in unique changes in skeletal muscle and endurance capacity that were previously believed to require hours of exercise each week.
A follow-up study confirmed the results. Despite the fact that the more conventional endurance exercise group spent 97.5 percent more time engaged in exercise, both groups of subjects improved to the same degree. The group that exercised 97.5 percent more received no additional benefit whatsoever from doing so. Considering the wear-and-tear and increased risk of injury associated with that much more exercise, there’s absolutely no point to doing “chronic cardio” when you can receive the same benefits with a fraction of the time and risk by doing HIIT.
The Cochrane study I linked to earlier in the article also found that high-intensity exercise was superior to “chronic cardio”. In particular, the researchers found that high-intensity exercise led to a greater decrease in fasting blood glucose levels than low-intensity exercise.
In his excellent book on high-intensity strength training,Body By Science, Dr. Doug McGuff also explains that high-intensity training is superior to chronic cardio because it produces a greater stimulus and thus more effectively empties the muscles and liver of glucose. This stimulus can last several days with HIIT, as opposed to just a few hours with low-intensity training.
HIIT also activates hormone-sensitive lipase (HSL), which mobilizes fatty acids for energy use. This means that during HIIT, both glucose and fatty acids will be burned, leading to greater fat loss and restoration of insulin sensitivity.
- Sit less. As a general guideline, aim for standing at least 50 percent of your day.
- Increase your non-exercise physical activity. Aim for 10,000 steps a day on average.
- Incorporate regular periods of more vigorous activity (exercise) throughout the week.
- 9 Steps to Perfect Health by Chris Kresser
- Body By Science, by Doug McGuff. The “bible” on high-intensity strength training. Goes into great detail on the physiological mechanisms and benefits behind this type of exercise, and explains how to put together a routine. Doug also has a great blog with an active community of people using the BBS approach. To see an example of what this type of workout looks like, check out this video on YouTube. For an in-depth video presentation about BBS, watch this video.
- The Power of 10: The Once-A-Week Slow Motion Fitness Revolution, by Adam Zickerman & Bill Schilley. This is more of a nuts-and-bolts book, with less theory than BBS and more focus on teaching you how to do this type of workout. It also has specific routines that can be performed at home, on the road and without access to a gym. The approach is slightly different than what’s advocated in BBS, but the basic idea is the same.
- You Are Your Own Gym: The Bible of Bodyweight Exercises, by Mark Lauren. If you prefer to train at home I recommend checking out this book!
- Bigger Leaner Stronger: The Simple Science of Building the Ultimate Male Body
- Thinner Leaner Stronger: The Simple Science of Building the Ultimate Female Body