If metabolic rate changes due to caloric restriction then this doesn’t negate the view that basic physics dictates that calories in minus calories out determines weight loss. It just means that a corresponding change to calories out can occur with caloric restriction. It is a physical reality that calories in minus calories out determines weight loss. It is also a reality that adhering to this might be very difficult for reasons you suggested.

If you want to increase muscle mass, why don’t you just keep lifting increasingly heavier weights?

If you want to lose weight, just keep eating increasingly less calories.

Because that trivializes the problem. There’s physiological pushback on many dimensions.

I suggest a better response to CICO is not that this isn’t true but that it is hard for a variety of reasons. One’s response to CICO ought not be to deny basic physics. There was a comment that it is basic physics that CICO is true and it got pushback. My post was to point out that the pushback against that comment were wrong in the sense of not actually disputing CICO.

The responses should have been of the form, “Absolutely but this is very hard for some people for the following reasons…”. That changes to one part of the equation can have unintended consequences that change the other part.

Here’s a quote from Kevin Hall, who does metabolic studies at Harvard:

>The problem is that CICO as the law of energy conservation is NOT a model of obesity. It's conflated with the straw-man "Conventional Model" described by Ludwig: independent, unregulated intake and expenditure implying that getting fat and treating obesity are all about willpower

It's not so much that I would dispute the physics, but I personally wonder about digestion. This strict cico model seems to make the assumption that every digestive system extracts the same amount of energy from the same foods, which I find unlikely but am certainly not an expert. If I eat a bunch of grass, I am pretty sure I'll probably get sick and have some unpleasant bowel movements but I won't draw many calories from the grass. Unlike a cow.

Personally though, I find it rather easy to maintain a particular weight. I just wear pants with the right waist size and if they feel tight I take it easy on eating for a day or two. I have had the same weight +/- 1.5kg for 20 years. Losing weight beyond my comfortable baseline is exceedingly difficult though.

That's not really how I interpret it at least. I think its assumed there is no one with a perfectly efficient digestive system, and that there is variance in efficiency based on a plethora of factors. However, that efficiency rate hardly matters. You are in effect a car. Some people are hybrids, super efficient perhaps, while others are SUVs guzzling gas to go the same distance. That being said one thing is true for all of these cars: if you put in 9 gallons instead of 10 gallons into the tank, you will go for less miles than if you put in 10 gallons. In other words, if you are being accurate about measuring your calories in (the gas) and you are measuring your weight (miles driven), you can adjust the input calories to effect your output weight. Exercise then is like driving in low gear with the engine at a high RPM; you are burning more calories in a given amount of time just like you'd be burning more gas in a given distance running at a higher RPM.

Nobody is contesting the physical reality of CICO; what they are contesting is that the "calories out" section of the diet is as easily controlled as previously thought.

I'm supposedly on a 1500 calorie deficit, eating ~1300-1500 calories a day and burning ~3000, according to my fitbit. But I'm only losing about 0.5lbs per week.

My conclusion is that I'm really only burning 2000 calories despite HIIT 3x/week, strength training 4x/week, and cardio 6x/week. If it weren't for all this training I would likely be gaining weight on what would otherwise be a reduced calorie diet for someone my size per every major TDEE calculation

>Nobody is contesting the physical reality of CICO; what they are contesting is that the "calories out" section of the diet is as easily controlled as previously thought.

I'm not so sure about that, I see a lot of claims otherwise on this article's thread which blows my mind a bit.

It's definitely an issue calculating and managing the calories out portion and for some people, it may not be an effective model to manage weight with diet and exercise, but I'm reading a lot of "this model is wrong" which is a little baffling to me.

Is it possible the caloric measurements are off? Absolutely, we may not even be considering all metabolic pathways, but hopefully a lot of its getting covered. CICO should be used as anchor points to help you guide your diet and find what works for you because everyone is a little different. Don't like a lot of vegetables, coffee make you sleepy and lazy? Hate cardio but love weight lifting or vice versa?

Try something else, but CICO can help you make a better grounded basis of comparison here to find what mixture works best for your body to manage weight and get or keep the body composition you desire. Does the model simply not work for your lifestyle? Try something else! But is it wrong? Eh, I don't think so.

CICO while thermodynamically true, is not _that_ useful because no one really control CI nor CO …

Both your calories in numbers and calories out are subject to extreme estimation error.

Also body composition changes can make “weight loss” difficult as you replace fat with muscle. You can also get a gross estimate of muscle/water/fat mass to see those changes (or go get a very accurate measurement a few times in a facility equipped for such things).

This is generally the correct answer.

Online TDEE calculators almost always overestimate expenditure, as do smartwatches. On the intake side, people lie to themselves constantly. First, they generally don't actually weigh their portions. In the rare event they really are weighing their food, they'll "accidentally" load up 4.3oz of something, then input it into their tracker as 4oz. Then they'll neglect to log their sauces and condiments, because it's "only" 20kcal for a tablespoon. These discrepancies add up.

Invariably, these ridiculous claims come down to people being liars, not just to others, but to themselves.

I did a strict 1400 calorie per day diet for a few months in college. Zero cheating. Also kicked up aerobic activity a ton.

Losses were at like 5-10% the rate they "should have" been. Totally worthless.

Meanwhile weight lifting has always worked for me a large multiple as well as it "should", for weight loss, if you go by calculators that try to figure how many calories an activity burns.

I reckon that in both cases those two approaches must be having large (and opposite) effects on my resting metabolic rate.

Aerobic activity is not all the same either. Some people run for a mile and think that's good, they are maybe burning only 300 calories doing that though. They hike for 4 miles and its another couple hundred, or its blown with the granola bars. If you bike for an hour at less than 10mph you are burning like 300 calories, but if you bike for an hour at like 16-20mph then you are burning like 1000 calories.

Unlikely you'll be burning 1000kCal at 16-20mph unless you're going up a steady incline and keeping that speed (i.e. high power). That is a bit of an exaggeration. The remainder of your point stands - cycling is a great way to burn a lot of calories.

You'd have to be pushing 250-300 watts an hour to burn that much, but people do burn that much in an hours time if you look around a few bike forums. If you have time to do a long and leisurely ride, 3 hours or so, the length of the new Avatar movie, you'd probably knock out at least 1000 calories imo. Whats nice about a road bike in particular for caloric burning, at least in my experience, is that it makes you want to push the bike and go as fast as you can and keep snapping up through your gears and catch up to the cars (passing them even when they hit traffic or you are descending).

At 25% efficiency (on the high side), 1000kCal is about 1050kJ, which is just shy of 300W. Most adults can't sustain 300W for an hour. In addition, reasonable riding conditions (flat, low to moderate winds) will get you moving faster than 20mph at 300W. Most adults are definitely not burning 1000kcal riding a bike for an hour and even fewer are doing that rate of calorie burn for longer than an hour. I regularly have >1000kcal rides, but I have yet to hit 1000kcal for a single hour at my highest intensity. I can do close to 300W for 20 minutes after which time the power drops off rapidly. Larger cyclists that are trained can absolutely sustain 300W for an hour, but won't do this without a significant training effort.

I don't mean to imply that you won't burn a lot of calories cycling, quite the opposite, I think it is one of the easiest and gentlest ways to do so. You are however overstating what most non-elite cyclists can regularly accomplish in terms of calorie burn per hour.

Source: I have averaged 450hrs/yr for last 3 years and closely monitor my data.

What people do believe is that you can neatly tabulate calories in and calories out.

Tabulating calories in and weight out is a lot easier, especially if you eat healthy and simple foods.