You may have noticed the headlines from a new study recently released in JAMA Internal Medicine in the popular media recently. It has appeared with titles such as:- “Maybe that workout can wait till the weekend?” (CNN)
- “Weekend Warrior Workouts tied to longer life.” (Reuters)
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“‘Weekend warrior’ workouts are as beneficial as just 20 minutes of exercise a day” (Newsweek)
When I see headlines like these I get a bit nervous. Whenever the media tend to get a hold of research they do their best to distill the results into as few words as possible. At best this misses a lot of the nuance of the research and at worse is downright misleading. One of my goals with the WLCR is to help you understand the facts about how your body works with respect to weight loss. This mission includes explaining research articles like this one so you don’t get misled.
When I read these headlines in particular I was particularly concerned that people would misinterpret the message of the study. I was worried that people would think they can get away with exercising less than is currently recommended by most medical associations in the world. So let me explain it for you.The study was an analysis of surveys completed by more than 60,000 Brits over an 18 year period to see how different exercise patterns influence the risk of death. The subjects were divided into three groups
- Regular Exercisers were defined as those that exercised several times a week to get at least the minimum recommended amount of activity (at least 150 min/wk of moderate-intensity aerobic activity, at least 75 min/wk of vigorous-intensity aerobic activity, or equivalent combinations)
- Inactive folks were defined as not reporting any moderate- or vigorous-intensity physical activities.
- Weekend Warriors were those that reported at least 150 min/wk in moderate-intensity physical activity or at least 75 min/wk in vigorous-intensity physical activity from 1 or 2 sessions.
The results showed that the Regular Exercisers were 35% less likely to die during the study period than those that were inactive. They were less likely to die of cardiovascular disease and cancer individually as well.
What was interesting is that Weekend Warriors were also about 1/3 less likely to die during the study period compared to people who were inactive. The study seemed to show that vigorous exercise improves fitness more than than the same amount of moderate intensity exercise. To learn more about the specifics of how vigorous exercise is so effective read this.
The conclusion you absolutely cannot make from this study is that you can get away with less exercise and still be healthy. This study defined weekend warriors as those that do 150 min of moderate or 75 min of intense exercise in 2 sessions. That is more time and intensity than most people are doing. While the “weekend warriors” had fewer minutes of total activity they actually had a higher proportion of minutes of vigorous activity. They were more about quality than quantity.
There were significant weaknesses in the study design that limit more broadly definitive conclusions.
- It was done in a relatively homogeneous British population so it may not be true for other ethnic groups.
- It was an observational study. Observational studies can only tell you that two things are associated but not that one causes the other. It may be that an unmeasured variable between groups is the true reason for the association not the exercise. Maybe people who exercise more do so because they are already healthier. Maybe these folks are more compliant with diet and medications.
- Most importantly, the measured exercise time and intensity was based entirely on the reports from memory of the individuals completing the surveys. Any data based on memory is notoriously subject to recall bias. People have fuzzy and sometimes distorted memories especially when it comes to remembering their diet and exercise history. There is ample evidence showing that people significantly overestimate their activity (read more about this here) so I worry that the conclusions may be skewed.
- This study did not mention the affects on weight so you can’t say which form of exercise is better for weight loss.
The clear conclusion you can make from the study is that all outcomes are better in those that exercise regularly than in those who are sedentary. This study also supports prior research that high intensity exercise is better the light or moderate exercise.
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