Research suggesting 60 minutes of cardio is no better for weight loss than 30 minutes is being touted around the media right now. But is that what the study really concludes, or is there more to it than that?
Some interesting research has hit the mainstream media recently (here’s The Telegraph’s take on it) which suggests that 60 minutes of cardiovascular activity is no better for weight loss than 30 minutes. The Danish researchers have even concluded that they have grounds to “challenge the basis for the current recommendations regarding exercise for weight management”.
We could simply trot out the old saying that if it sounds too good to be true then it probably is, but despite the fact that the average research paper is about as easy to comprehend as Arabic, Navajo and Klingon combined we thought we’d give it the once over and see if there really was anything in it.
The gist of the research’s full text was this: Two groups of guys (20-40 yrs) exercised every day for 13 weeks at the same intensity, but one group trained for 30 minutes whilst the other group trained for around 60 minutes.
It seems that there was no significant difference in fat loss between the two groups, with the 30 minute group losing more actual weight (3.6kg) than the 60 minute group (2.7kg). Herein lies the first snag with the idea that less is more: the corresponding fat loss measurements were 4.0kg and 3.8kg respectively, which suggests that whilst the 30 minute group put on 0.4kg of muscle, the 60 minute group put on 1.1kg – over twice as much.
As we know, lean muscle plays a huge part in the amount of fat that we can burn, so over a longer study might we expect the 60 minute guys, with their higher muscle content, to pull well ahead? They would certainly fare better in the short term were both groups to stop exercising altogether.
Clearly it is possible that a short burst of high intensity exercise could provide more benefit than a longer burst of lower intensity exercise, and the research has at least gone to some lengths to ensure that intensity of exercise was constant across the two groups, but have they ticked enough boxes?
To try and regulate the intensity, they used a gizmo called an Actigraph GT1-M, which is essentially a step counter but with a few more bells and whistles, enabling it to measure different formats of physical activity (walking, running, rowing, cycling etc.). Aside from the fact that this device only appears to have been used on five days of the thirteen week trial, some 2010 research from Edinburgh on the accuracy of the Actigraph GT1-M and other such devices suggested that it underestimates step count by some 2.5 METs (Metabolic Equivalents; a unit of measurement for exercise) per minute.
More significant perhaps in terms of the researchers’ attempts to measure intensity is the use of heart rate and its associated formula.
The ‘Heart Rate Reserve’ calculation (Maximum Heart Rate = 220 – Age) is a notoriously unreliable way of determining exercise intensity. Two people of the same age, resting heart rate and exercise experience can and will find training at any given heart rate a completely different experience in terms of the rate of perceived exertion. The experience will differ again according to their choice of equipment – with more aerobic activities like running producing a much higher heart rate than that returned on, for example, a cycle – even with the same amount of effort.
Also, anyone who uses a heart rate monitor on a regular basis will know that exercising at any given heart rate becomes easier the longer one exercises for. This would suggest that the 60 minute group could quite easily have been exercising at a lower rate of intensity for at least the second half of their workout.
The researchers also made some efforts to ensure that diet did not play a major factor, whilst being keen not to eliminate the possibility that the 60 minute exercisers might simply undo the benefits of their extra half hour by gorging their faces once they got home. Calories and their macro-nutrient composition were measured very accurately, including a deduction for leftovers, but it does appear that diet controls were only in place for 15 days of the 13 weeks.
On the subject of control, it also appears that a margin for non-adherence to training of some 20% was allowed. So up to one in five days training could be missed – more relevant if you make the understandable assumption that the 60 minute group would yield a more frequent chorus of “I can’t be bothered today”. Such days were of course recorded, but can we be sure that all test subjects owned up? They were not required to submit heart rate monitor data for every day.
Aside from the above flaws in control, any of which could significantly influence the results given the relatively small number of participants, it is when we try and compare the research strategy used versus everyday life examples that we find room for perhaps even more significant flaws. Both groups trained every day for 13 weeks. Every day? Who trains every day? Even elite athletes take the odd day off, so could the results of our group of 60 minute novice exercisers have suffered more from over-training than the 30 minute group?
A far more relevant and more easily controlled test would be to have got our two groups of exercisers to train three times per week with at least one days rest in between. Given that 60 minutes of pure cardio is fairly unusual for the average exerciser, another more relevant comparison might be between say 20 minutes and 40 minutes.
At best this research suggests that mildly overweight men (not women) aged 20-40 who are new to exercise are better off keeping their cardio sessions a little shorter, but any claims beyond that – particularly in terms of current recommendations about exercise duration – should be considered boastful.
Could it be that experienced exercisers will gain more from exercising for longer? Can the clinically obese expect different results? What about women? Older men? The study most certainly doesn’t answer these questions one way or another. Having said that, the team at Copenhagen University should be commended for at least trying to isolate the results of each group of exercisers.
At worst however, our Danish researchers may have unwittingly added fuel to a fire that continues to burn out of control while it warms the couch bound masses. Although for some the notion that less is more might be enough to drag them off their backsides and into the gym, for many others it will just reinforce the misconception that if they keep on biding their time, from somewhere within the fog of fitness industry misinformation, a road will eventually appear to them that really is signposted ‘Easy Street’.
What do you think? Is 30 minutes of cardio really going to be better than 60 minutes for weight control, or is the research too flawed to draw that conclusion? Let us know in the comments below…