The idea of working out in the ‘Fat Burning Zone,’ sounds great in theory – if you want to lose body fat, you need to moderate your exercise intensity so as fat is the predominantly fuel ‘burnt’.
It sounds straight forward enough, however it’s not really the most efficient way to reduce your body fat.
The Fat Burning Zone
So the idea of the ‘Fat burning Zone’ isn’t where this theory is flawed. It is absolutely correct that at low/moderate intensity exercise, you will use more fat to fuel your exercise then if you were to workout at a higher intensity (where glucose/glycogen become the predominant substrate).
In fact, working out at around 50% of your VO2 max you will burn around 50 – 60% fat (and 40 – 50% glycogen/glucose; with a significant allowance for individual variances), compared with working out at around 75% of your VO2 max, which burns around 35% fat (and 65% glycogen/glucose). (1)
Better news still, at rest you burn around 66% fat – so you don’t need to exercise at all, you’ll burn fat in your sleep! Clearly this isn’t helping anyone lose weight.
(Note, this is a very simplified explanation of a complex physiological process)
Increase your intensity
Although while working out at around 50% of your VO2 max you burn a greater percentage of fat, your overall energy expenditure and thus overall fat use, will be far less than when working out at a higher intensity which achieves a greater overall energy expenditure in the same timeframe. (That is, 35% fat from a bigger energy expenditure is more than 50% fat from a smaller energy expenditure.)
It is possible to achieve the same energy expenditure from low/moderate intensity training as higher intensity training however you will need to work out for far longer and unfortunately you will still not reap all the same weight loss benefits of high intensity training.
To give you some figures to put this concept into perspective we can look at a study of the effects of a High Intensity Interval Training (HIIT, think hill sprints, squat jumps, burpees) protocol compared with a continuous aerobic exercise protocol. This study showed that after 15 weeks of HIIT training participants lost 13.9mm of fat (based on skin fold measurements), compared with only 4.5mm after 20 weeks of a continuous aerobic exercise protocol. (2) What is particularly interesting in this study is that participants in the HIIT group lost far more fat, despite expending significantly less energy during their training program (remembering that the HIIT group exercised for 5 weeks less). Once adjustments were made with the data from this study, the overall effect on skin folds (as a marker of body fat) from the HIIT group was 9 times that of the continuous exercise group, which is quite impressive.
So as I said, even with matched energy expenditure, or in the case of this study greater energy expenditure, the same weight loss benefit of high intensity training is not achieved – but why??
HIIT training is more effective for weight loss, even when matched for energy expenditure with low/moderate intensity training because of a little thing called EPOC (Excess Post-exercise Oxygen Consumption). EPOC basically means you have an oxygen debt to pay back to your body after you finish exercise which comes at an additional energy cost.
So although the energy expended during a HIIT session might be less than an aerobic workout in the ‘fat burning’ zone, thanks to EPOC as much as 95% of energy expended can occur after the workout while you repay that oxygen debt. This ‘after burn’ has been reported to last for as long as 48 hours!
In addition to EPOC the metabolic adaptations which occur with ongoing HIIT appears to have long term additional ‘fat burning’ (beta oxidation) benefit. That is, remember how I earlier said to allow for large individual variance in ‘fat burning,’ well this is why – with ongoing HIIT your body become better conditioned to using fat a fuel.
What’s not to love about HIIT!
Don’t get me wrong
This is not to say that low intensity exercise isn’t worthwhile, it’s simply saying that if weight loss is your goal than high intensity training is a better use of your time.
A further clarification still, if you are just starting out on your weight loss/ exercise journey a low intensity program can be very beneficial to ease your body back into exercise and reduce the risk of injury and/or the risk of you quitting the program before you’ve reaped the benefits because it is too hard and you struggle to move for days after.
So by all means, start off at a low intensity and as your fitness, confidence and motivation increases start to build your intensity to get the most out of your workout time (it’s always a good plan to get medical clearance before starting a new exercise regime).
A bit more bang for your buck
In addition to your HITT training (or lower intensity cardio equivalent), adding some strength exercise to your workouts will help give you more ‘fat burning’ bang for your buck.
But strength training, like lifting weights, will make you bulky, right? … Well that’s another myth for another day =)
Gluten free diets are being hailed for their role in weight loss, and much, much more...
There was a lot of ground to cover in this month’s myth bust, so it will be coming to you in a two part instalment. Part 1 clears up some background information about what gluten is and why people might avoid it for medical reasons while Part 2 looks at those other reasons people are avoiding gluten, like for weight loss and general health - enjoy
Part 2: Why else go Gluten free?
Beyond the conditions discussed in Part 1 of this monthly myth bust, gluten has been branded as the cause of weight gain, general feelings of lethargy, poor health, and inflammation which underpins heart disease, diabetes, cancer, and arthritis, amongst other things. Consequently, the hyped reasoning to avoid gluten includes increased energy levels, aiding weight loss, and a general “healthy” or “lighter” option.
With this impressive health resume, does a gluten free diet live up to the hype - Should we all be avoiding gluten?
As we’ve seen so far the evidence for specifically avoiding gluten beyond Celia Disease is limited and yet ordering from the gluten free menu seems to be the new “I’ll just have a salad …”
Weight loss is quiet possibly the biggest preoccupation of our modern western society and of course we would just love to find something to ‘blame’ for our population-wide weight worries (other than poor dietary choices, limited physical activity and generally being immersed in an obesogenic environment) – enter Gluten.
We’ve tried blaming carbohydrates, we’ve tried blaming fat and we’ve tried blaming sugar, next on the chopping block is gluten.
The underlying mechanism by which gluten is blamed for weight gain is inflammation, which is also said to be the reason it causes heart disease, diabetes etc. There is evidence to support the inflammatory effect of gluten in people with Celiac Disease, as is to be expected, and even a little for those with NCGS, despite no clinical markers currently being accepted. (1) But within the general population the evidence is (again) limited.
The one and only study which seems to be quoted as the ultimate ‘evidence’ that gluten causes weight gain in subjects without Celiac Disease or NCGS, claims that removing gluten from the diet of mice reduced inflammation, insulin resistance and adiposity (fatness), compared with mice fed a high fat diet (61% of energy from fat), comprising 4.5% gluten, however this diet is hardly reflective of the typical Western human diet, or even the recommended diet (e.g The Australian Dietary Guidelines), so the beneficial effects of a gluten-free diet as claimed by this research, seems a bit of a stretch (but of course more research is warranted). (2)
The benefits of a gluten free diet in the general population is further questionable given that another study on human subjects with hyperlipidaemia, reported that increasing wheat gluten on a weight maintenance diet reduced triglyceride levels by 13% independent of fibre content, suggesting that gluten may in fact have some benefit in improving lifestyle related conditions. (3) Of course, we could then consider the plethora of data to support the beneficial role of whole grains, including wheat and other grains containing gluten, in type 2 diabetes, heart disease, some forms of cancer and weight management. (4)
The fact is there is insufficient data to support any of the widely made claims the gluten causes weight gain, hampers weight loss, or causes inflammation, diabetes or heart disease within the general population.
So despite a few mice seemingly benefiting from removing gluten from the diet, do I think cutting gluten from your diet should be the first lifestyle modification made to aid weight loss or improve lifestyle related conditions? Umm, No…
Ultimately if people have lost weight by ‘going gluten free’, more than likely they have just cut their carbs, which we know results in short term “weight loss” largely from water losses. We know that a low carb diet results in no greater weight loss after 6 months than other dieting methods (such as low fat, high protein etc) and is difficult for many to sustain long term.
So if you are stocking the pantry with gluten free products simply to lose weight you are wasting your time, your money and could actually be risking your health.
Negative Consequences of avoiding Gluten
Resistant starches in grains like wheat (which we know contains gluten) creates healthy gut bacteria shown to reduce the risk of some cancers, inflammatory conditions, and cardiovascular disease. (3) Given the dependence on wheat in the western diet a significant portion of resistance starch comes from wheat consumption and as such following a gluten free diet unnecessarily could have adverse effects on gut health. Conversely positive changes in gut health as a consequent of including whole grains in the diet have been seen within as little as 3 weeks. (3)
Despite the hype around gluten there certainly is no reason for the general population (outside of having a gluten related disorder) to jump on board this movement. Cutting gluten from your diet to improve your overall health, prevent disease or aid weight loss is not substantiated by current research and in fact, gluten could in fact have some health benefits. Although the research to support this is far from definitive, the role of grains in good health is definitely well understood. Of course branching out from wheat, irrespective of gluten, adds nutritional variety to the diet and assists to increase crop biodiversity so by all means enjoy a variety of grains, gluten free or otherwise, within your diet too.
- Celiac’ s must adhere to an exclusively gluten free diet
- Our understanding of NCGS, and specifically the role of gluten in this condition, is very primitive
- There is insufficient evidence to say that a gluten free diet has any positive effect on conditions such as MS, schizophrenia, dementia or autism
- There is similarly little evidence to say that a gluten free diet causes any harm in these conditions
- There is insufficient evidence to say a gluten free diet has an effect on weight loss, obesity, inflammation, insulin sensitivity or diabetes
- The gluten free food industry is cashing in on processed products that are equally energy dense and nutrient deficient as their gluten containing counter parts
- Whole grains are good for us and many of them just happen to be gluten free
This is a really great fact sheet that guides you through the spectrum of gluten related disorders including symptoms and appropriate diagnostic protocol. (open fact sheet)
The Monthly Myth Bust
Using research and evidence to bust and debunk all those Nutrition and Fitness myths you've been wondering about.