If cycling is mostly aerobic, why can weight loss affect sustained power so much?

I know from personal experience that you can train really hard but if you diet hard at the same time everything just falls apart. Why is that? Basically just energy requirements, or is there a strong link between FTP and weight?

Conversely, if you took a 65kg rider with 200 FTP, and stuffed him with cake for 2 months so he got to 75kg, would he get a jump in his FTP if he was doing just maintenance intervals?

I don’t know but, I do know most of us average joe’s do a poor job managing calories while dropping weight. A few pro cyclist I know can do it but, they have help not only with a coach but, in some cases nutritionist etc…

With that said, and maybe going beyond what you’re asking, I did some digging and found the addition of fat mass did not affect absolute VO2max. Obviously it changes relative VO2max. But, more importantly especially to us hobbyist, an increase in fat mass decreases time to exhaustion in sub maximal aerobic activities.

This is my opinion and have no evidence to support what I write, but in a very general sense, “larger” riders have more muscle fiber. More muscle fiber = “more” power. So maybe FTP is a larger value but, like we’ve all experienced, TTE on climbs is poorer, acceleration is poorer, capacity is generally poorer.

Fascinating topic. Hopefully, a coach or physiologist will chime in that knows what they are talking about.

It’s not just the pure weight that gives you more power it’s the increase in muscle volume that does.
So cake would nog work but a boat load of protein combined with a proper weightlifting regime would work.

This is why tall riders can be good steady climbers and good climbers, ie Tom Dumoulin, Froomy and Poels.
They have that magic 2 pound per inch of height but that also gives them a huge ftp number, Tom Dumoulin’s being 450 after an oktober training camp.

So recap pure slow twitch muscle volume/weight helps you ftp not overall weight.

Chad brought up The Obesity Code by Jason Fung in one of the podcasts and that suggests the answer. Losing fat while training and making gains is possible over a long period with a modest calorie deficit. By dieting “hard”, which I take to mean having a large calorie deficit, will cause the body to react by reducing the base metabolic rate to match your intake and to not put on lean mass which is costly to maintain.


Not sure what you mean or where you started, my experience is that it’s possible to get stronger and lose 2-4 pounds a month for a total of 10-20 pounds. But I have plenty of body fat to lose, and am patient to slowly lose the weight.

FTP. by itself, really tells you nothing about the fitness/strength of the rider because of body size differences. It is the FTP/kg (Strength/Weight) that reveals the most accurate summary of fitness/strength. Obviously this important measurement will fluctuate with weight loss/gains and cardio and strength changes.

2-4lb a month seems reasonable if you have a decent amount of body fat to spare I’d say. Again, from experience I think that you need to lose weight slower as body fat % reduces. Not sure what the science is there either though.

I was doing a kilo a week some weeks and was going for around 3 months! Really extreme stuff now that i look back over TP and MFP. Was over 82kg and went to 71.3kg. Bodyfat at the end was hovering in the high 10% to low 11%. Must have been over 15 to 16% when starting though didn’t track that at the very start unfortunately.

If you look at what @rjessop was saying, that was something I experienced, but to an extreme. In the end I couldn’t get my heart rate up and felt like I was 90 years old and had to move around slowly. Even doing 150 watts felt like hell.

For a while I was worried I’d permanently destroyed my body, but things are back to normal and power returned funnily enough without much work. Just stopped training and started eating normally again. Interesting learning experience, I was doing the whole clean eating thing and using energy drinks to fuel workouts as that’s the only way you can really get the energy to even attempt a workout when your glycogen reserves are permanently shot!

Didn’t really want to get into my personal situation, but was hoping for more on the theoretical side of things. I do have tons of tracked data and info about my experience going hardcore earlier in the year, but would take hours of writing to even touch on what it was really like and what the numbers and power loss was and the workouts I was doing, and when the failing started etc…

Tell that to all the 3.5 W/kg climbers that I drop on the flats at 2.5 W/kg.


@rjessop Does he give any clue as to what the maximum weight loss/fat loss without losing power, or even gaining power is?

Ultimately, that’s what I’d love to know. I’m into week two of my base plan and going to lose some weight and have lofty FTP goals that I want to hit. Thinking to try -250cals a day this time, with Monday being slightly over.

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Fung doesn’t explore this as his book isn’t focused on athletes in training. However, friend of the podcast Matt Fitzgerald does explore this in his book The Endurance Diet. If I remember that correctly it’s basically not possible to run a deficit and get optimal fitness gains, but you can benefit from a weight loss phase of training if you are 10 or more pounds (for goodness sake people start using the metric system!) above your race weight. For this he advises a deficit of 300-500 calories, but increase your protein intake to about 30% of daily calories and make the workouts lower volume but a bit higher intensity. Treat weight loss phase and fitness phases of training as distinct with distinct goals, rather than trying to optimise both.

Take that with a pinch of salt, as like I said it’s been a little while since I read it!

This is too variable per person for there to be any universal answer.

Most folks tend to agree that you can get away with losing weight and maintaining fitness during the base phase but that it is nearly impossible with the higher intensity and demands of build or specialization.

Luckily - sweet spot is by far the most efficient way to burn calories so it is generally easier to accumulate a decent amount of calorie burn at the time when you are most able to run a deficit.

Ultimately you need to decide what your priority is - weight loss or fitness gains. For me - I try to get close to my target weight ahead of my build and then just float within a +/- 3 lb range for the entire build/specialize/race season. I will try to cut a bit when I’m riding less to make up for holidays and other weight gaining events but never to the point where it will impact my ability to complete the intervals


+1 to this. It also makes it easier in the following seasons to lose weight during base if you are at a higher starting FTP that has carried over from the previous season, since you’ll be burning more kJ.

Fung’s theory in The obesity code is that your set-point (read: the body fat percentage your body is trying to maintain) basically is determined by the insuline resistance/sensitiviy of your muscles, liver etc (their level of resistance can differ). Counting calories is not key there. I actually increased my overall calory intake and lost several pounds this year while raising my FTP. What and when to eat are the important questions.

You don’t loose fat alone.

Lose a little weight-loose only a tiny bit of muscle and you can build more than you loose. If you eat right.

Loose a lot of weight-loose more muscle than you gain, loose the same you gain? Depends on physiology and diet.

Crash diet, freak out your body and it will canabalize itself.

in my personal experience I’ve dropped about 24lbs (197 -->173lbs) and raised my FTP by 60w or so
( 2.5w/kg -->3.6w/kg) over the course of about 20 months. I started calorie tracking, training consistently (this is key), and in the latter portion of that time fueling my workouts with high quality carbs (this helped a TON). In my case I went from 18% to about 14.5% body fat, so I definitely had some to lose. The trick is try not to lose too much too fast, but still fuel your workouts. I believe that for most on a low-mid volume plan you can both have a calorie deficit and also fuel your workouts if you time things correctly, stay away from fried foods, and lay off the beer (much to my profound sadness). Of course this is an N=1 study, and I don’t know what I’m talking about :slight_smile:


Make it N = 2.

I’ve gone from 205lbs down to 156lbs over the past 3.5 years and my FTP has increased year over year each year. The key is to go slow and sustainable.

And yes, it’s really easy if you cut out the alcohol and fried food.

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DUDE thats freaking amazing, good work! I agree completely

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