One interpretation of the "calories in, calories out" model of weight loss is that you can simply "move more" - increase your activity levels - to lose weight.
Moving more has a diminishing return on effort over time, while also exposing you to greater risk of injury.
So in reality, while this can work, it's usually some combination of caloric restriction and movement that is most optimal.
If your goal is to lose weight, there's a slight bias towards diet being alone being more effective than exercise alone, but neither is ideal.
One of the common misconceptions about the meaning of the “calories in, calories out” (CICO) model of weight is that it can be boiled down to the simple “eat less, move more” maxim. First of all, it’s generally not nearly as simple as that, and there’s a lot of variables that can obscure your progress and make it hard to understand what’s actually going on. These very precise variables can often give you the impression that it’s really something else that’s responsible for your changes in body mass, even when CICO is actually working just fine.
“Eat less, move more” is a useless piece of advice - just like telling a depressed person to smile more, or by telling a basketball player that it’s easy to win the game by getting the ball into the hoop more than the other team.
Yes, the goal is ultimately to eat less and move more in a general sense, but the massive web of habits that need to be changed to make that happen is much more complicated than that. It’s insulting to try and boil that down to a single sentence.
Another common mistake is to focus solely on the “move more” end of the equation.
Some types of people would prefer to avoid diet altogether because they just don’t want to change what they eat - so they think, if the two halves of the CICO equation are equal, then why not focus on the part they can more easily change, the “calories out”. These people would gladly trade a bit of extra time on the treadmill in order to have a bit less strict of a diet, and would gladly take this to the ultimate conclusion of spending hours per day on the treadmill.
However, there are a lot of problems to this approach. Here are a few.
Boredom/Lack of Time
This approach requires drastic amounts of time. Whereas a bodybuilder or powerlifter can get by on about 5-10 hours of serious training per week and see awesome results in terms of strength and size, training to lose weight via exercise alone could take many times that. This means boredom, tiredness, and many hours spent in the gym. If you’re a person who’s limited on free time, this is the exact opposite of a high efficiency routine. So, chances are that you'll hate it.
Increasing Risk of Injury
The single greatest independent predictor of injury is more time spent training. It would be simplistic to say that doubling your time spent in the gym doubles your risk of injury, but it will definitely increase it by a huge amount. Once you get injured, your risk of reinjury also rises drastically, which can create a downward spiral of injury and dysfunction if you don’t take a cautious approach and use proper physical therapy techniques - and chances are, most people won’t.
The more you train, the more likely you are to get hurt - and this certainly isn't desirable.
Additive VS Constrained Models of Energy Expenditure
The classical model of energy expenditure is called the additive model - as you add exercise, your total daily energy expenditure (TDEE) rises linearly with additional exercise. More exercise is always better.
However, studies of very active populations show that this isn’t actually what happens - instead, there’s diminishing returns as you increase your exercise levels.How can this happen?
Being more active in your workouts burns energy that you would be using on other activities throughout the day - you’ve used up your energy already, so you’re less likely to spontaneously decide to move around. You'll feel less energetic, and more lethargic. You'll be more likely to sit down in front of your TV instead of going for a walk. This decreases your calories burnt from daily activity (NEAT).
Likewise, there are documented cases of athletes who train so heavily that their bodies begin to preferentially take calories that would normally be used on your base metabolism and start giving them to the higher priority - the energy that you HAVE to burn by exercising. So, sudden and large increases in activity, far from linearly increasing your overall energy expenditure, may LOWER your base metabolism because your body is cutting corners to make ends meet. Naturally, this will have negative consequences in terms of your recovery, in terms of your performance, and in terms of your long term health - your body wasn't made to have corners cut.
This graph should make it clearer, in case this is a bit confusing:
You Burn More Calories With Your RMR
Overall, the amount of calories that the average person burns per day is somewhere in the range of 1200-2500 calories. A serious, intense workout might burn about 300-600 calories per hour - but the more intense it gets, the more exhausting this will be. Realistically, you can’t keep up a very intense activity for very long - and the longer you train, the fewer the calories you’ll burn, in part because you’re more tired out and can’t keep up the same intensity of activity, and partly because of constrained energy expenditure (see above).
The end result is relatively simple - that you generally burn, on average, many more calories simply for being alive, than you do on working out.
You can try to burn more calories through activity, but this will just get more and more exhausting - your return on effort continually goes down. Days when you're not working out, you're not going to be burning nearly as many calories. A common mistake is to lose weight solely via exercise - and then, when you start to pull back and take a more moderate approach, see a sudden and huge regain of weight because you were relying on exercise alone.
The general truth is this - if the goal is to lose weight, it’s generally easier and less physically/psychologically stressful not to eat the food in the first place than to spend the excess time burning it off. It might take you seconds to eat something but a half an hour to burn it off - and most of us don't have endless time.
So, if the goal is to manage your weight, diet tends to be more valuable than exercise to begin with.
Heart Rate Monitors Are Inaccurate
I’ve covered this before in my post on quantified self and related devices, but here’s some more recent research that also points out just how inaccurate many heart rate monitors are. Heart rate straps are generally accurate, but most other heart rate monitors (including wrist-based and the handheld ones that you find on your gym’s treadmill) aren't.
This means that you may easily be misled into thinking that you’re burning more calories than you actually are - leading to a false sense of the importance of the contribution of cardiovascular exercise to the “calories out” part of the equation.
So What Should You Do Instead?
People tend to lose weight far better on a specific kind of program - a greater focus on diet than exercise, with regular, small amounts of exercise just to keep your metabolism high and to maintain muscle mass while you lose weight.
Note how, in the graph above, everything looks like it progresses linearly, in the beginning, before it starts to level off. That's the point at which you start getting diminishing returns to additional activity. So, working out a little bit (and regularly) is clearly a bit better than cranking up your duration endlessly and pushing yourself far into the "pointless diminishing returns" zone.
Simply adding more activity is not optimal. It may work well for some, but is more likely to cause harm than good.
Hell, in most cases, people don't need to lose much weight, if any, to begin with - rather, they just need to start training regularly.
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- MASS Research Review... Review
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- Ignore Those Absurd Diets If You Want Real Results
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- Weight Management: A Simple And Comprehensive Guide
- Calories Matter, Even When You Think They Don't
- Programming Your Macros Part 1: General Health And Wellness
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