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Comment by geoduck14 | Hacker News Reader

>A lot of people know this already, so it’s not busting everyone’s myths

It is still worth mentioning - because it is so easy to overlook.

Some simple math: if I go all out on a row machine for 30 minutes, I'll burn 300 calories.

If I eat 2 extra slices of pizza, it is easiely 300 calories

If I swap a turkey sandwich with healthy options, I can reduce my linch calories by 300 - and I can save even more during dinner (which is typically bigger than lunch)

So a good diet: takes less time than exercise, reduces calories more, and can save money

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> if I go all out on a row machine for 30 minutes, I'll burn 300 calories.

A stationary bike at a steady 20mph pace is about 500 calories in 30 minutes. That's really significant. An hour will erase about a third of a normal person's diet.

When I used to do heavy training (long distance running, weight training) I would eat close to 8k calories a day and I was in fantastic shape. Eating more was necessary to survive, given how much energy I was expending.

An hour will replace a third of a healthy persons diet.

Fats are the secret to obesity, hands down. I have a remarkably small appetite and I can easily down 1000 calories of ice cream in a single sitting (a single pint of Ben and Jerry's. You can row like crazy for 30 minutes, but if you have two extra candy bars, it's meaningless.

Avoiding calorie dense foods is big, yeah. But exercise is exercise and at higher levels (1+ hour/day) the caloric burn is very significant compared to baseline metabolic rates.

Yes, our bodies are built to take in more calories than we can burn (thankfully!), but if you keep your eating habits constant the exercise will make a huge difference.

Most people can't manage to burn 1000 kcal in a 60 minute workout. I am a large man in fairly good shape and have to put in a pretty hard effort to hit those numbers. People who are smaller or not well trained are going to be significantly lower.

Measuring stationary bike workouts in terms of mph is kind of meaningless. What actually matters is the measured power output based on the resistance setting.

I'm a 40 year old guy who's been sitting behind a desk writing software for two decades. I was in good shape in my 20s but haven't exercised significantly in a very long time.

It took me about three months to get up to that speed, cycling every other day. I started out doing 10 miles, at 10mph.

Three months isn't all that long for an exercise program.

same here, I'm in my late 20s and was generally unhealthy because of the pandemic, and I burn 630-700 calories per 30 minutes worked out

That is unlikely. How are you measuring calorie burn? You're probably overestimating.

As a point of comparison, an average size man would have to run at a speed of at least 11 mph (18 km/h) in order to burn that many calories in 30 minutes. Not impossible, but well beyond what most of us can manage.

Not that it matters, but reporting mph for a stationary bike (indoor trainer I assume) is meaningless in this context. This could mean that you're cycling anywhere between 0 and 2000 Watts.

I cycle on and off for ~8 years (35yo) and going at 20mph in the real world for an hour or more became possible only after a few years for me.

Color me skeptical. In order to burn 1000 kcal in 60 minutes a cyclist would have to sustain a power output of about 280 W. Do you have a calibrated power meter, or are you going by the "vanity" calories displayed by most stationary bikes?

There are certainly plenty of trained cyclists who can maintain that power output, but I've never seen anyone reach that level after only 3 months. If you really did that then you're an extreme genetic outlier with an unusually fast training response.

I don't know, actually. I'll check it out later today. I do know my heart rate is around 150-160 throughout.

I did a lot of cycling in my 20s and while I'm at least a decade out of shape I'm sure I'm relying a lot on past training.

High aerobic fitness evaporates pretty quickly. The training you did a decade ago will not carry over to today. However, there are a few genetic outliers who can quickly build up a high level of fitness with just a short training program. You could be one of them, but it's more likely you're just getting bad data.

Absolute heart rate doesn't tell us much about calorie consumption because there's a huge variation between individuals. If we know the athlete's size, sex, and threshold heart rate then we can start to make some kind of estimate. But to get an accurate number it really takes a properly calibrated power meter (or more complex lab tests involving exhaled gas measurement).

It seems doubtful the measurements would be far off. The numbers fit with the expected 50 or so calories per mile biked.

It's doubtful that your measurements are even close to accurate. If you're on a stationary bike then the distance displayed is completely meaningless. The equipment manufacturers just show those numbers to make their customers feel good. In terms of calories they are in no way comparable to real outdoor cycling. You can get a great workout on a stationary bike but you need to be realistic about the true power output.

What is the actual power output in watts? Has it been properly calibrated? If not then you're just fooling yourself.

"Completely meaningless" and "in no way comparable?"

These statements are rather extreme and seem impossible to support. Energy output per mile with real world cycling has enormous variance as well. Why so much concern for precision regarding one and not the other?

I don't think there's much point in continuing here.

I'll continue with one last comment just for the sake of others who might be reading. The "distance" displayed on most stationary bikes is calculated by counting flywheel revolutions and multiplying by some arbitrary factor. It has no real correlation with the actual distance you would cover by pedaling a real bike with the same effort. It's a totally pointless number that tells you nothing useful about caloric expenditure, but some customers want to see it so the manufacturers put it on the display.

You can get an accurate calculation of real world cycling calories with a power meter. Everyone's cycling efficiency in terms of power output per calorie burned falls within a fairly narrow range so converting from time and watts to calories is simple. A good power meter accurate to within a couple percent can be added to any bike for about $700.

Smart trainers like a Tacx Neo or Wahoo Kickr also have accurate power meters built in. Those are substantially different from typical stationary bikes.

fwiw, I checked and the bike does have a power meter, I think it's an RS3 Lifecycle (or some similar model). I do a sustained 220-250w for an hour.

I understand the translation between power and mph is somewhat approximated, but I think you could be more generous. It's not unreasonable to make this kind of approximation and the numbers aren't meaningless.

>A stationary bike at a steady 20mph pace is about 500 calories in 30 minutes

It is also something at most a tiny minority of the obese population can do.

I just plugged a 300 pound person in to a calculator for a “moderate” walking speed, and that’d burn nearly 500 calories in an hour.

Most 300 pound people I know cannot walk for an hour at a moderate walking speed.

You are severely overestimating the physical abilities of a severely obese person.

> A stationary bike at a steady 20mph pace is about 500 calories in 30 minutes. That's really significant. An hour will erase about a third of a normal person's diet.

That assumes a “normal person” will not compensate for the effort with a snack.

A “reward” pint of ice cream will re-add more calories than the hour of cycling. A “standard serving” will nearly match your half hour.

And that’s an hour at 20mph, which really isn’t in any way the norm.

> That assumes a “normal person” will not compensate for the effort with a snack.

You're also assuming the same normal person will not compensate for their healthy lunch with a snack.

>An hour will erase about a third of a normal person's diet.

Pretty sure most people shouldn't be eating 3000 calories/day.

Probably not, but the average American does eat about 3600/day.

But what if I like pizza?

The thing is, the 300 calories from rowing shouldn't be compared to the absolute calorific requirement (say 2500 calories) but the surplus. So Maybe I'm overweight because I need 2500 and I eat 3000. Thats 500 too much, but take out 300 and that's 60% of what I need to at least reach equilibrium. It makes a huge difference to how much I need to sacrifice out of my diet.

A few hours on my bike can be 2,000-3,000 additional calories over base metabolic rate. That's not based on made-up calories but actual work from a power meter on the bike.

"You can't exercise your way out of a bad diet" - literally not true for a fuckton of endurance-sport athletes for whom the challenge is eating enough calories.

It's 100% true for people who think exercising for 30 min means license to eat whatever.

> So a good diet: takes less time than exercise, reduces calories more, and can save money

Yes, but endurance exercise over an hour or two brings its own advantages health-wise.

The real takeaway is that there are no absolutes.

Looks at wahoo kickr in corner

Hello old friend, we meet again.

One of the cruel aspects of endurance sports is that they suppress your appetite. You can go out and burn 6000 calories in one race, spend the whole time thinking about all the delicious food you're going to reward yourself with, and then you get there and have zero desire to eat. You sometimes can't even start refeeding until the next day.

Feels to me like pushing your body to extremes is akin to a metabolic shock and your system rebooting in another operating mode. Probably needs another reboot to go into regular mode, so your apetite will also vary in the meantime

I always feel there are some methodology issues in sports science studies like small sample sizes or strange metrics.

While I do agree with you that sustained, high level activity requires and burns more calories, I think that the advice coming out of there, exercise is less efficient than diet for weight loss, is going to absolutely be true for the majority of gym goers who quite frankly are phoning it in whenever they work out.

Like, for example, an olympic swimmer may eat 5000-10,000 calories in a day, but they are spending around 4-6 hours a day in a cold pool training at a world class level (body needs to keep warm somehow regardless of effort.) But a normal person may only swim for 20 minutes at a much gentler pace. This person should still be eating in line with calorie guidelines and macros for age/sex.

The reality is that diet needs to be flexible based on results. Not losing weight? Eat fewer carbs or calories. Feeling tired and worn out? Eat more or exercise less based on your physique and goals.

For the majority of regular people feeling tired and worn out is more likely to be caused by lack of sleep and too much booze than by lack of food or excessive exercise.

I meant more from training hard for long term. Most people are not at this level or pushing that hard. Normal people would definitely benefit from lifestyle changes outside of the gym if they are tired and worn out.

If I remember correctly, Olympic swimmers are NOT spending 4 hours a day in the pool, and certainly not 6.

https://www.reference.com/world-view/michael-phelps-training...

A couple of years ago I took swimming lessons from the Swiss butterfly swimming champion and he said he trained about 20 hours a week and that to get to Olympic levels, he'd have to train even more. For swimming it's possible to train much more than in other sports, because it doesn't do as much joint damage, because you're in water.

I spent years failing to lose weight through diet. I took up endurance cycling and in one day (13 or 20 hours) I burn off a kilo or more, even with the increased eating. Afterwards I'll put that back on in about two months, but as long as I keep doing one or two of these events every month I come out ahead.

I don't know how things are for anyone else, but it worked for me, shrug.

I had very similar experience. I lost weight with no much additional effort when I started to do a lot sport. I did not focused on food much, I was doing sport for weight loss unrelated reasons. And it dropped.

Attempts to loose weight by diet only all failed. To make it worst, there is also aspect of most common diet advice being plain wrong. It focuses on calories too much. It completely ignores what your body needs, so you end up in nutritional deficiency - this kind or that kind. And that will affect a lot and eventually you will stop diet and start to feel so much better and healthier after stopping it.

> I always feel there are some methodology issues in sports science studies like small sample sizes or strange metrics.

The calorie stuff is from both oxygen and deuterated water studies. You burn the same amount of calories and your system just shunts them around. The science on this is one of the few things in nutrition that is quite solid.

This has the effect, for example, that if you exercise a lot, this actually suppresses your immune system making you more likely to get sick.

After a 2000 kcal high intensity cycling workout I'm so tired that I don't even feel like eating. I have to force myself to eat something because I know I need it for recovery.

> A few hours on my bike can be 2,000-3,000 additional calories over base metabolic rate.

Are you sure? 2000 kcal in 3 hours is 770 watts of power output.

Edit: Wikipedia [0] says "During a bicycle race, an elite cyclist can produce close to 400 watts of mechanical power over an hour and in short bursts over double that - 1000 to 1100 watts; modern racing bicycles have greater than 95% mechanical efficiency. An adult of good fitness is more likely to average between 50 and 150 watts for an hour of vigorous exercise."

[0] - https://en.wikipedia.org/wiki/Human_power

You are forgetting that the human body is nowhere near 100% efficient at burning fuel to put power into a pedal. To produce 400 watts of mechanical power, the body consumes about 4 times that amount of fuel (25% efficiency). Consuming 2000 kcal over 3 hours is thus closer to the more realistic 200W of power to the pedals, and even the higher ranges make sense if he's a good athlete. See this article: https://www.welovecycling.com/wide/2020/05/14/how-to-convert...

> You are forgetting that the human body is nowhere near 100% efficient at burning fuel to put power into a pedal.

I'm not, because the parent poster explicitly said "That's not based on made-up calories but actual work from a power meter on the bike."

Which seems absurd, hence my comment.

It is a very valid point that dieting / food intake converts to calories way more drastically than exercise.

The article is taking this one step further though and saying those 300 calories burned by exercise are simply conserved elsewhere throughout the day automatically by your body.

The claim then is that if you exercise and burn 300 calories, but eat an extra 300 to offset it you won't end up at a neutral state and instead will gain weight as if you hadn't exercised at all.

In your example, if you exercise, you can have the pizza as well as the sandwich. This can be significant, because suppose you have those 300 surplus calories 3x/week minus the exercise (not unreasonable, a small snack here and there, right?). 300 calories is about 3 bananas, so it might not even be unhealthy food.

Rough math: 3 * 300 * 4 = 3600 calories surplus/month. A pound of adipose tissue has ~3500 calories IIRC. So you're now gaining a pound of fat a month, and you're not even indulging yourself, really.

In reality, physical activity and diet aren't so steady, so some months you maintain weight, some you lose, and some you gain a lot. But over time it averages out, and you've put on 12lbs in a year.

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