In part 1 we looked at some good reasons why you might want to do steady cardio but we left the arguments about fat burning to this second instalment.
The fat burning arguments about the two options go like this. HIIT ramps up your metabolism and helps you burn more calories in the hours after exercise (the ‘after burn’) so that you end up burning more calories than you would have done in a steady state cardio session. The steady cardio argument says that at moderate intensities the body’s fat utilisation is maximised so it makes sense to exercise at a moderate intensity for a decent length of time in order to burn off some fat. Hmmm, they both kind of make sense don’t they?
Let’s look a little closer. To pick this apart we need to understand fat burning in a little more detail. You can consider fat burning as a two stage process
- Get the fat out of where it is stored.
- Use it for fuel (oxidise it).
There is a process that connects these two, which is the transport of fatty acids in the blood and across cell and mitochondrial boundaries, but we will ignore that for now to keep the discussion tidy.
HIIT is great at getting fat out of fat stores. It does this by ramping up adrenaline, which causes the breakdown and release of fatty acids from fat stores. However, HIIT is pretty poor at oxidising fat. It’s well known that at high intensities the body’s choice of fuel is almost entirely carbohydrate. That said, HIIT will make your metabolism hum for some time afterwards and so will burn extra calories in a much lower intensity zone where fat is more readily utilised for energy.
Steady cardio is not so good at getting fat out of the stores, but does a pretty decent job of oxidising it, since at moderate intensities the body more readily uses fat as a fuel. On cardiovascular machines such as treadmills and elliptical machines, you may see ‘fat burning zone’ on some of the available programmes, evidencing this well known property of human energy metabolism. You have to go at it for a longer time and a you will not get the same ‘afterburn’ as with HIIT, but as you become fitter you will be able to work at a higher intensity in the fat burning zone and so burn more calories.
So which is better? First, I want to say that either choice will help with fat burning. To some extent, the choice may be a matter of preference. For example, if you are short on time, you might find HIIT a better choice. If you have a bit more time and want to be able to watch the TV while you exercise, then you might prefer steady cardio.
Steady cardio is my preferred choice. I do it first thing in the morning in a fasted state. Here are the reasons why I advocate this approach.
- First thing in the morning your body’s hormonal environment is optimised for getting fat out of fat stores. Growth hormone and testosterone are up, glucagon is up, insulin is right down, cortisol is up (in the absence of insulin). This combination means your body is already breaking down fat for fuel by the time you wake up. Do some steady cardio and you can burn off a lot of that fat that is being released. It has also been demonstrated that fat oxidation is improved in the fasted state.
- If you take in some caffeine prior to your cardio then you will also ramp up adrenaline for even better fat release. I take 2 or 3 spoons of coffee about 30-40 minutes before my cardio.
- It has been shown that regular aerobic exercise up-regulates enzymes associated with fat oxidation. That means you get better at using fat as a fuel as a result of regular steady cardio. That doesn’t just apply to the period in which you perform your cardio, that applies generally throughout the day. You get better at using fat as a fuel. This is particularly important for formerly sedentary individuals or those with metabolic diseases whose fat oxidising efficiency may be reduced.
- With early morning fasted steady cardio, it matters less what your body uses for fuel for the rest of the day because you’ve disposed of a decent amount of fat during your cardio session. With HIIT, whilst you might be burning more calories for some time afterwards, who’s to say those calories are coming from fat? In fact, there is strong evidence that fat oxidation is reduced for many hours after a meal so the chances are you are not oxidising as much fat as you had hoped.
- Steady cardio first thing in the morning is muscle sparing. What!? No really, it is, for two reasons. First, the hormonal environment first thing in the morning is all about fat utilisation. The body has a preference for releasing and oxidising fat and so will be less likely to touch your precious protein stores. Second, because practising steady cardio makes you better at oxidising fat, your body is more likely to use fat for fuel during the rest of the day, rather than choose to derive energy from precious muscle protein. If you are bad at oxidising fat and are getting a large portion of your calories from protein then, guess what? Your body gets better at using protein as a fuel. Eat the optimal amount of protein and get good at oxidising fat and you can minimise the amount of muscle protein that is broken down for fuel.
So you can see there are a lot of reasons why I am a fan of steady cardio. Now, before you go off and label me ‘steady cardio guy’, I want to be clear that my main thing, my obsession, is weight training. In reality, my label should be more like ‘weight training guy’. I am a firm believer that any exercise programme should include weight training. If you can only find time for one thing, do weight training. If you can do both then the right combination of weight training and steady cardio can do wonders for a person’s body composition.
There is definitely something to be said for HIIT’s ability to ramp up the metabolism and burn calories for a longer period, but I prefer to see my weight training sessions as my form of HIIT. Done with sufficient intensity, a weight training session is far more potent than an HIIT session in creating an after burn. Couple that with the fat oxidation benefits of steady cardio and you have a great combination for favourable changes in body composition.
Don’t get me wrong, I’m not a detractor of HIIT. If it works for you and you like it, then do it. I even use it myself in combination with steady cardio when I am trying to get to very low levels of body fat. It has its place.
I should conclude by saying that none of your cardio efforts will make a difference to fat loss if you are not maintaining a calorie deficit. That is a prerequisite. Get that right and you will lose weight. The trick is knowing how to make sure all that lost weight is fat.