We Need to Rethink Exercise (Updated Version)

Losing weight is hard and unfortunately your  body is sabotaging you every step of the way. Your body is a biological machine that follows  the laws of thermodynamics and needs energy and raw materials to stay alive, which is why you eat.  The energy from food is measured in calories and you need a certain amount to power your internal  machines.

Your brain thinks, your heart pumps, your gut digests, your immune system immuns.  And you contract your muscles to move around. The harder a movement is, the more calories you  burn.

An hour of walking burns about 260 calories, moderate swimming 430, biking 600, running 700. If you eat more calories than you burn, your  body stores them mostly in the form of fat. One kilogram, or two pounds, of fat is about  7000 calories.

Seems simple. To lose weight, you have to burn more than you eat,  so fat is turned back into energy. There are two ways to do this: Eating less – which  we will cover in another video – and burning more, say by moving around aimlessly, also called  working out.

We also get told early on that exercising is healthy somehow, so working  out should kill two birds with one stone. Unfortunately this doesn’t exactly work out.  It is one of these frustrating experiences where you do what you think is right only to  not see the results you deserve.

In reality, focusing on exercising is not  a reliable way to lose weight. Some studies show that exercise  can lead to some fat loss, others that it is minimal. How  can this be?

It turns out that until recently we fundamentally misunderstood  what moving around a lot does to our bodies. Disclaimer: The science on fat loss  is complicated and many studies compare vastly different populations, different  measurements and are complicated to understand. And the online discussion is full of personal  anecdotes.

This video covers general principles, based on the current state of research.  But when you look at the individual, there are variations – it matters if you are  an athlete or casually try to lose weight. The Myth of the Workout A few years ago scientists began to compare  populations in industrialized societies, which sit a lot, to hunter-gatherer  communities, who move around a lot.

The Hadza people in Tanzania walk an average of  9 km a day to find wild plants and hunt animals, dig for tubers, climb trees for honey,  or collect water. They can move more in a single day than an office worker in a week.  So of course, they burn more calories, right?

But it turns out that the Hadza burn the same  amount of calories per day as a typical person in an industrialized country: around 1900 for  women and around 2600 for men – which doesn’t make sense at all. It’s also not their genes, since  it’s the same for other hunter gatherer tribes. So the confused scientists looked at similar  measurements in individual countries.

It got even stranger: Active people who work out  regularly do burn more than inactive people. But only very little, often as low as 100  calories, the equivalent of a single apple. For some strange reason in the long term, the  amount of calories you burn is often relatively unrelated to your lifestyle.

Per kilo of muscle  weight, your body has a relatively fixed calorie budget it wants to burn per day. Sure, if  you want to gain muscles by pumping iron, you also need to eat more to build and sustain  them or your new muscles wither away. But in total, your body keeps your calorie  budget per unit of you, pretty stable.

And to make matters worse, if you want to lose  fat your body sabotages you in small and big ways: First of all, when you begin to work out  regularly, maybe going for a run in the morning, your body may subconsciously make you move  less when you don’t pay attention. Maybe you take the elevator instead of the stairs, you  sit more when you meet your friends or you sleep longer – largely balancing out your burn  again, preventing you from burning much fat. You can overcome this temporarily: If you do  actually change your life after sitting around for years and suddenly start working out without  eating more, this is a shock to your system.

You actually do burn more calories and lose fat – so  you can lose weight through exercise! But this is often very short-lived. Your body adapts and burns  fewer and fewer extra calories each week until it restores its original calorie budget.

After a few  months you burn a very similar amount to what you did when you didn’t work out. If you stay really  consistent your burn might increase slightly and your body composition might change, but most  people struggle with keeping up the habit, if they don’t love the extra movement. Which  is why so many people hit a weight loss plateau Objection!

What about muscles? Muscles burn 3  times more calories at rest than fat. This sounds impressive, but tissues like your brain, skin  or intestines burn way more.

In absolute terms, a more muscular body composition makes a  difference for how many calories your body burns, but it’s relatively small.  Muscles matter a lot for health, longevity and performance, but  not that much for weight loss. Bizarre.

And now we are getting to the  actual reason why exercise is healthy. Why Your Body Is Sabotaging You So your body has an activity budget per  day that it wants to stick to. This setting evolved when humans had to move a lot. 

Not because they wanted to, but because they had to find food for survival. But when  food is abundant and exercise is voluntary, what does your body do with the energy  that you are not using to move around? We are simplifying a lot here and this is  relatively new science, but in a nutshell: There are many different systems in your  body trying to do their job as well as possible.

And if there’s extra energy, they  seem to use it. Unfortunately this is bad. When your immune cells detect injuries  or infections, they trigger inflammation.

Fighter cells, alarm chemicals and fluids flood  into your tissue. This is crucial but it also causes damage, so it needs to be cleaned  up quickly or it can become chronic. And chronic inflammation is one of the major  contributors to many serious diseases, from cancer to heart failure.

If your  immune system is on a tight budget, it has to be efficient with inflammation – with  lots of free calories though, it over commits. Another thing is that your glands produce  hormones you don’t need. Like cortisol, the stress hormone, which triggers your fight  or flight response.

Crucial for survival, but if you have too much of it you get, well,  very stressed, all the time. Chronic stress is a major cause for a bouquet of health issues  including your mental state. For our ancestors who moved a lot and had to deal with sudden  bursts of activity, fleeing from a lion, attacking that bison, this cortisol was crucial  – but if you live a modern, sedentary lifestyle your body is ready for action that doesn’t  happen, hurting itself in the process.

Your body evolved to move regularly  and is fine tuned to a certain base level of activity. If this activity  is missing it still uses almost the identical amount of energy, just on  stupid stuff. This is why you burn a similar amount of calories whether you  work out or not.

A lot of the energy you spend working out is energy you don’t spend on  other physical activities and body processes. Working out is not a magic bullet, but it seems  to restore an internal physical balance that seriously affects your body. And this is also  why regular exercise is so incredibly healthy, the evidence is incredibly clear here.

It  reduces chronic inflammation and stress, it is good for your heart, may ease depression,  and makes you live longer and better. Why Humans Are So Hungry When your ancestors evolved, they had to work  hard for calories. Sometimes it would be easy and they could afford to chill out quite  a bit.

But in hard times they had to move quite a bit to feed themselves, walk longer  to find prey, or dig longer to find tubers. If extra movement burned more calories this  would lead to a spiral of starvation. The less food you find, the more energy you need  to find food – which doesn’t even fill you up, because you moved more.

It’s like  taking on more debt when you are in the red. It works for a while, but then you  go bankrupt and die. So for your ancestors, being able to move a lot without burning  extra calories was a matter of life and death.

Ok. But this means the obesity epidemic of the  modern world is not primarily caused by laziness, but by overeating. Humans evolved  to be mad for calories.

Because of our extremely hungry brains,  and our extremely useless kids. Kids are cute but unlike other species,  human kids have to be fed and cared for by adults for years before they become  even remotely useful. Because the human brain not only eats up about 20% of all  our calories at rest – twice as much as our closest ape relatives’ – it also takes  a lot of time to develop through playing, learning and honing social skills –  all the things that make us human.

Our species is so extremely calorie-expensive  to maintain that we became super-efficient calorie harvesters. 5 hours of human hunter  gatherer foraging yields between 3,000 and 5,000 calories, while our ape relatives  get no more than 1,500 in the same time. And we became so good at calorie harvesting  precisely because of our big brains and years of social skill training.

In a typical  ancestral tribe some members would spend the day searching for plants, others hunting  or gathering honey, others nurturing kids. And at the end of the day, we’d share the  calories so that no one would end up hungry. Being frenetic calorie harvesters seems to  be deeply part of what makes us human.

It's not a bug, but a feature. But today it  seems as if that feature has turned on us – we can’t stop overproducing food,  and overeating. If you want to lose fat, reducing calories is the biggest part of the  answer.

We’ll cover diet in the next part. So to conclude: You will probably not lose  nearly as much fat by working out as you hoped, but you will do something more important:  give your body balance and make you more resilient and prevent or delay many of  the diseases that will make your life miserable so you can enjoy a higher  quality of life, for much longer. But physical fitness is only half the equation. 

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