We ran a poll asking which type of workout was best to lose weight and here's what you said

So it would seem that we tend to favour the harder work over the longer, lower intensity work.  This is quite counter to the 'low intensity, fat burning zones' that are on many of the cardio machines in our clubs.

So what gives?  Are we mad, or do we see in practise something that isn't in the text books.

To answer this question with a bit of science lets first look at the 'volume' involved in each of these workouts.  By multiplying the average intensity (in this case gained by using the average effort or Rating of Perceived Exertion) by the duration you get the volume of work done.  In order: the weights workout was a 9/10 x 20 minutes = 180; the intermittent workout was a 6/10 x 30 = 180; the walk/jog was 3/10 x 60 = 180.   Obviously RPE is not 'gold standard' accurate but has a reasonable validity, enough to shed light on this topic anyway.

So, all workouts involve about the same amount of work and therefore will require about the same amount of ATP to fuel - meaning the same amount of calories should be burnt during the workout.

Given the workouts are all about equal in terms of caloric cost we should then consider what the energy cost of recovery might be.  Recovery is the period post workout until the body is fully repaired and back at homeostasis (resting).  Most significantly a higher intensity workout causes more fatigue, a greater shift from homeostasis and more damage to the hardware of the body.  Thus, the resistance workout would take the longest time to recover from and would use the most calories during recovery as a result. 

We should also consider which workout changes our hardware (muscles, bones, tendons in this case) the most affecting our metabolism over the longer term.  Again, in this case, weight training should cause a gradual change in FFM (fat free mass) or LBM (lean body mass) to be more accurate.  Given our BMR (basal metabolic rate) is influenced by our LBM we are in effect developing a bigger engine with which to burn calories.  So the weights harbour more long term change in caloric consumption because they should result in more muscle mass.

It would seem weights are of great benefit.  But there are counter arguments.

Improved aerobic fitness allows us to burn a larger proportion of fat at any given intensity, and as we get 'fitter' we are likely to be more active as well.  So, one could argue that despite the more intense workouts being of greater caloric cost (when considering recovery cost and long term LBM changes) the aerobic workouts would allow us to exercise more often and burn, during any activity, a greater proportion of body fat (much of this achieved due to the adaptations in the muscle allowing for greater use of fats as fuel).  Maybe low intensity aerobic workourts are the best approach afterall.  As we get fitter, we can burn more fat, we are more likely to exercise more often.

Then you could close the loop and argue that a middle ground, where muscle adaptations caused by moderate to high intensity overload and cardiovascular adaptations caused by 'intermittent' activity would be best - an optimal mix of intensity and duration.  Well, you might be right. 

But what are we missing here?  We're missing the fact that although you can make the science fit for  most types of workouts, by far the most effective workout ever prescribed is the one the client will do consistently enough to get the result.  In this regard there is no singular answer to the 'best workout for fatloss' question.  The exercise science is quite simply irrelevant until you frame it out by knowing who's asking. 

So, next time you get asked this question, answer with a 'why would you like to know'?  You might find there's a client behind the question, and with their background and preferences captured, the answer becomes infinitely simpler.