I have lost count of the number of supposed products and tips that I've read about recently as ways to supposedly boost or 'hack'' your metabolism. As if your biochemistry is an algorithm to be tricked. If only you have access to the secret code, you can switch into turbo mode and simply out-metabolize a bad lifestyle...
It is easy to see the appeal. No need to start any drastic diet, eat those pesky vegetables or embark on one of those sweaty gym programs. Just eat some spicy foods, drink an iced drink, or turn the thermostat down a few degrees and make your metabolism work harder! (all actual tips that have appeared in my inbox in the past few weeks). Unfortunately it is not quite as simple as that....
A short but important diversion - on interpreting scientific findings
I love science - it is my background, and at the core of my approach. So I don't like to be negative about it - however it is important to be aware that, in amongst the vast amount of great work being done in this field, unfortunately there is also a lot of bad use of science. And in large part, we have this to blame for the proliferation of 'Ingredient X leads to Metabolic response Y' thinking.
In interpreting scientific studies, it is important to be aware that a statistically significant finding is not the same thing as being clinically significant - or having relevance in real life. A statistically significant result simply means that there is enough of an effect, under controlled circumstances, that the researchers would not put the results down to chance.
So whilst it may be possible to demonstrate a 'statistically significant' raising of metabolic rate in a laboratory environment in response to a single food or nutrient, often the effect is actually very small - and is also highly unlikely to be replicated in real life, when the vagaries of the rest of our diets and lifestyles come into play (for example, we had the spicy food but that made us crave sugar afterwards, swiftly undoing any negligible metabolic 'boost').
Reported results are also based on statistical averages, which can mask high degrees of bioindividualty (or metabolic variation) between individuals - which can be huge! We have different sized livers and kidneys doing the metabolic work; different length and shaped digestive tracts,; Muscles, brains and hearts with vastly different demands. Not to mention an entirely unique microbiome to ourselves. You will never meet another individual who metabolizes the same as you!
It is therefore not always a straightforward matter to extrapolate the scientific findings to what will happen to Mr A. Actual Person if he adopts regime Y - because his own diet, lifestyle, history and yes, metabolic characteristics will come into play.
So what happens outside of the laboratory?
When we adopt a new regime - whether calories in or calories expended - we tend to see a metabolic response in the short term in terms of metabolic rate and / or weight changes. This is what the majority of research studies will report i.e. findings from one point in time. 25g of Nutrient X raised basal metabolic rate by Y%.
However this is short lived. Studies that do look at longer term effects show that beyond approximately two weeks , any effects begin to diminish, and the growing consensus is that that is because metabolism is not a 'fixed formula' - but responds to the stimuli it is given.
This is not to say that metabolism is not influenced by diet. But that the absolute effect is often temporary - and smaller than we are led to believe. One interesting - and well-designed - recent study at NIH (CITATION) NEEDED compared the metabolic response to a keto vs plant-based diet, and showed that even when strictly adopted, the difference in calories expended under these diets, amounted to no more than 100 calories per day.
In fact, the only thing that we appear to be able to do reliably is to make our metabolism slower by clogging it up with processed foods, not exposing it to the diverse range of real foods it was designed to for - or challenging it with sufficient energy demands (activity). Fortunately, this slow down is also reversible.
In the mean time, the existence of the studies lends credence to those who stand to benefit from highlighting those relatively small changes as if they were a magic fix - notably food manufacturers who love being able to slap a 'backed by science' label on the latest turbo charged smoothie ingredient, sexy spice mix or whatever. Drink it in your undies and freeze outside for double the metabolic challenge!
(IMAGE?)
Back to basics
It would serve us better to skip the over-simplistic, single food or dogmatic diet metabolism 'hacks' and instead focus on strong foundations for metabolic health. It is really about getting back to basics and - as so often - the things we all probably know, deep down...
#1 - Eat a good range of real food
It is essential to utilize all three fuel sources (protein, fats, carbohydrates) for optimum 'metabolic flexibility'.
Regularly cycling between the different metabolic pathways is the best way to build your 'metabolic muscle' - allowing you to efficiently switch between fuel sources as they are available. This is one of the key tools that I like to use - basing the schedule on your bioindividuality and actual experience, rather than statistical averages.
#2 - Take sufficient (but not excessive) exercise
For a long time, it was assumed that more exercise = more energy used. However it is now clear that this relationship is not linear.
There is growing evidence that some kind of threshold exists in terms of metabolic expenditure. Multiple studies show that we see shifts in metabolic rate at the greatest levels in populations at the lower end of the activity scale. Increasing activity will result in greater expenditure. BUT - only up to a point. As activity levels increase, the law of diminishing returns kicks in, as it seems, our metabolism adapts.
This finding also fits with bodies of evidence that show that there is a poor relationship between different societies (or even different species) in terms of activity levels and caloric expenditure.
In fact, it has been found that some of the most active populations in the world, such as the Hadza people of Tanzania (75 mins vigorous activity per day!) do not have higher total expenditure than the (famously inactve) US (few of us meeting the recommended 75 mins per WEEK).
This is because there is a plateau - each species operates optimally within a relatively fixed range, of energy expenditure beyond which we go into survival mode, finding ways to use less energy, which may deplete reserves for other functions. For us humans that optimal range is thought to be in the region of 2000-3500 cals per day (depending on body size, gender, lifestage).
#3 - It's (always) all about balance
This might all make you think that there is little point in making changes to our diet or lifestyle i.e. if our metabolism simply adapts to whatever we do. Yet there remain many - incredibly important -benefits of supporting the bodies own drive towards homeostasis with a well-balanced diet and regular, moderate exercise.
As we all know, excess - or unused fuel has a habit of being stored in the body, often in unhelpful ways. Another theory ('Calorie Constrained Energy Expenditure) is that the body will try to expend unused energy by 'overspending' on processes such as over-producing hormones, or engaging in excess immune or inflammatory activity; also unhelpful.
Regularly 'draining the metabolic battery' with sufficient - but not excessive - exercise therefore enables a full recharge, without taxing other bodily systems too heavily - and supports whole-body homeostasis - or balance.
Contact me to find out more about my - science and real life - based approach to building strong metabolic foundations.
Thanks for reading!
References
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3910615/?report=reader
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