Weight Loss Discussion Thread

[Wowbagger]

My Sunday Morning Weigh-in has me at 111.4 kg, a loss this year of 8.6. There was one glitch when the scales read 110.8, but I think I can afford to ignore the glitches now and concentrate on a figure the scales repeat often enough to make it credible, so 111.4 has gone on my spreadsheet.

[Lady Cavendish]

MFP grossly overestimates calories burned.

I'm amazed at the amount people reckon they are burning on rides. 50 miles I reckon only earns me about 1100 (granted, I'm a 58kg female but even still, there are some massive numbers being thrown around). Even for a 200k Audax, I only get about 2,500-2,700

[L CC]

we were riding for 12 hours yesterday. My 85 kg counts that as 6000. It'd be less if it was warmer and/or flatter, and less windy. It doesn't really matter, as even I would be hard pushed to eat all of them.
I've always found audax days ok, it's not eating so much in the days afterwards  when The Hunger strikes that's the struggle.

[Feline]

MFP grossly overestimates calories burned.

I'm amazed at the amount people reckon they are burning on rides. 50 miles I reckon only earns me about 1100 (granted, I'm a 58kg female but even still, there are some massive numbers being thrown around). Even for a 200k Audax, I only get about 2,500-2,700

Actually MFP does not, but you need to decide on whether to put in the minutes as light, moderate or vigorous based on how much effort you think you consistently put in rather than the speed. Doing 12 mph uphill on a mountain bike is clearly not equivalent to doing 12mph on the flat on a road bike with a tail wind. If you read back above you will see that Simon has compared MFP's estimates with actual measured power output using a Powertap and found it to be largely accurate. What are you basing your estimates on? Heavier people and people with more muscle mass that is metabolically active burn off more calories, and males burn off more than females. If you think you can ride 50 miles and only burn off 1100 calories then you must either have a very efficient metabolism or you are cruising along the flat on a lightweight bike behind someone else because you would burn off 1100 just lying in bed all day!

[Lady Cavendish]

I did a study for Someones research project at a lab in Twickenham. The given figure for running is 100 cal a mile, I was burning 70. My OH who is 6 foot and 11 stone burnt 110.

Cycling to work I average a HR of 140 for the 70ish mins that it takes. (ave speed normally about 16-16.5mph) With all their gadgets that was found to burn 410 Ish. It's an undulating route, not flat. My Audax HR is lower than that and so if harder cycling is about 370 per hour for me, Audax must be less. Therefore even if being generous and saying 340, 12 hours would only earn me 4000. I normally average 9-9.30 riding time (more like 3000)- and I think 340 is generous compared to cycling to work effort.

They are just my figures though- and I struggle to lose weight even using those figures and still staying green on MFP.

[Lady Cavendish]

Oh yes and forgot to mention the cycling to work figures were on my heavier bike with full pannier on. I'm much lighter for Audaxes.

[Feline]

Oh yes and forgot to mention the cycling to work figures were on my heavier bike with full pannier on. I'm much lighter for Audaxes.

Yeah, I am using the 'light' cycling figures for my lighter weight bike regardless of how fast I ride it, and 'moderate' for my heavier winter bike with its fat tyres or ice tyres on. There is a possibility the fitter you are the fewer calories you burn doing the same thing I suppose. I have stamina but don't consider myself very fit. My average heart rate is about 170bpm on most rides, partly because of asthma. I don't know whether this means I burn more off, or whether it just makes me sound like I am about to expire on ascents but with the same calorie burn. I seem to be losing weight at roughly the rate MFP says I should be for what I'm eating and logging so far.

[simonp]

I did a study for Someones research project at a lab in Twickenham. The given figure for running is 100 cal a mile, I was burning 70. My OH who is 6 foot and 11 stone burnt 110.

Myfitnesspal doesn’t give a constant 100 calories per mile, it adjusts it based on weight, though not enough to explain all that discrepancy. For your OH’s weight, it says 113/mile and for yours, 93/mile. Running economy is a big factor in running pace and energy consumption, though.

I used my power tap yesterday and it says I output 2530kJ over the whole ride. Even being very generous, that can’t be less than 2500 calories for 70 miles, and doesn’t allow anything simply for the time spent cycling in addition to the output at the wheel, and assumes muscle efficiency at the high end.

[hellymedic]

LadyCavendish's figures are very similar to those I found I was using when commuting and Audaxing. Never had MFP (or even a PC) then. 400kcal/hour when cycling quite hard usually meant I had the weight/bonk balance right. (70kg female)

[Lady Cavendish]

Sorry Simon I didn't mean MFP gives everyone 100 cals a mile. I didn't explain that at all well. I mean its what u read generically in all the magazines/books about running.

[simonp]

Sorry Simon I didn't mean MFP gives everyone 100 cals a mile. I didn't explain that at all well. I mean its what u read generically in all the magazines/books about running.

Yeah I guessed it was an 'average' figure. MFP does better than that by accounting for your weight but it's not the only variable.

[DrMekon]

I used my power tap yesterday and it says I output 2530kJ over the whole ride. Even being very generous, that can’t be less than 2500 calories for 70 miles, and doesn’t allow anything simply for the time spent cycling in addition to the output at the wheel, and assumes muscle efficiency at the high end.

What do you get if you just convert the watt-hours to kcal?

[simonp]

I used my power tap yesterday and it says I output 2530kJ over the whole ride. Even being very generous, that can’t be less than 2500 calories for 70 miles, and doesn’t allow anything simply for the time spent cycling in addition to the output at the wheel, and assumes muscle efficiency at the high end.

What do you get if you just convert the watt-hours to kcal?

You mean not allowing anything for efficiency? That'd be about 1/4, or 625kCal.

[mcshroom]

I'm a little confused with that. A 'calorie' in dieting terms is actually a kCal. So the powertap is saying you burnt 625 kCal above normal activity in that time?

[simonp]

I'm a little confused with that. A 'calorie' in dieting terms is actually a kCal. So the powertap is saying you burnt 625 kCal above normal activity in that time?

No, more like 2500 plus some. Detailed answer follows:

The powertap is saying that I output 2530kJ of work in that time. This is 625kCal, roughly (it's actually a little less). However that is output energy not input energy (which is what food calories - kCal indeed - are).

Before I used livestring and then myfitnesspal I tended to assume that 1kJ => 1kCal, i.e. canceling out the 4:1 division. This approximation assumes that the 4.2:1 ratio between a kCal and a kJ is roughly cancelled out by the inherent efficiency of about 25% in human energy matabolism. Hence the figure I would have used would be 2530kCal.

From wikipedia:

The efficiency of human muscle has been measured (in the context of rowing and cycling) at 18% to 26%. The efficiency is defined as the ratio of mechanical work output to the total metabolic cost, as can be calculated from oxygen consumption. This low efficiency is the result of about 40% efficiency of generating ATP from food energy, losses in converting energy from ATP into mechanical work inside the muscle, and mechanical losses inside the body. The latter two losses are dependent on the type of exercise and the type of muscle fibers being used (fast-twitch or slow-twitch). For an overal efficiency of 20 percent, one watt of mechanical power is equivalent to 4.3 kcal per hour. For example, a manufacturer of rowing equipment shows burned calories as four times the actual mechanical work, plus 300 kcal per hour,[17] which amounts to about 20 percent efficiency at 250 watts of mechanical output. The mechanical energy output of a cyclic contraction can depend upon many factors, including activation timing, muscle strain trajectory, and rates of force rise & decay. These can be synthesized experimentally using work loop analysis.

Note the 300kcal/hour constant used by Concept II on the rowing machine. I think you have to assume an increased energy burn from cycling over and above that purely attributable to mechanical power (e.g. it takes more effort to ride an electric bike than to lie in bed). I'm not sure how much we can attribute to that but it can't be zero so there must be some additional energy consumption above that ~2500kCal that I can't directly measure.

[zigzag]

fwiw, riding sitting on a spinning bike for 30min i burn about 400 calories at 270w average, which would translate to 800cal/hour. however that's pretty damn intense and i'm not sure if i could sustain this average for an hour, let alone longer.

for long/audax rides i reckon my output average is 150-180w (not tested, but comparing perceived effort), which is 450-500cal/hour. aformentioned 70miles ride is done in 4hr when ridden vigorously (~27kph), so calorie count for me would be ~2000.

what i'm intersted in is if doing different excercises (e.g. running, swimming, rowing etc) at the same heartrate burn the same/similar amount of calories.

[simonp]

150w * 3600 secs / 4200 (joules per kCal) / 0.25 (efficiency 25%) => 512kCal/hr

180w * same => 617kCal/hr

270w * same => 925kCal/hr

How do you obtain the calorie figures you're using? The 150w-180w range is about what I've measured for my Audax riding, and I think you're faster than me. I averaged 160w or so on Saturday, but that was spending 1/2 the ride in a bunch, and power was very variable.

[spenceey]

80.9 kg yesterday.

Knee is still hurting but hopefully I'll be seeing someone (private or otherwise) about that before long. Planning on a couple of rides this weekend, will ibuprofen it up and hope for the best.

Absolutely determined to get below that 80kg mark, last Monday I was below it but imagine that was just dehydration.

[simonp]

I'm 69.6kg today. I tried to eat all the 3500 calories mfp said I burned but I fell 1000 short and I only managed to break even yesterday.

[Lady Cavendish]

I'm not sure its necessary to force feed yourself calories just because MFP says you burn them lol.

My appetite has started to come back, but the figures I've been using seem to be losing me a bit of weight consistently so this is good news Happy with this

[zigzag]

<...>
How do you obtain the calorie figures you're using? The 150w-180w range is about what I've measured for my Audax riding, and I think you're faster than me. I averaged 160w or so on Saturday, but that was spending 1/2 the ride in a bunch, and power was very variable.

i wouldn't say my figures are very accurate, more like rough estimate. over last couple of years i had a go on different spinning bikes, turbo trainers, rowing machines, treadmills where i enter my weight and the display shows watts generated and calories burnt. i am going to triathlon show this weekend where i'll see how i manage on powerbar 5k indoor time-trial. i am currently partaking in performance study (by british olympic medical institute), which should give me very accurate data about heart rate, watts, calories, vo2 max, lactate etc.:



a bit off topic this post..

[mcshroom]

I'm a little confused with that. A 'calorie' in dieting terms is actually a kCal. So the powertap is saying you burnt 625 kCal above normal activity in that time?

No, more like 2500 plus some. Detailed answer follows:

The powertap is saying that I output 2530kJ of work in that time. This is 625kCal, roughly (it's actually a little less). However that is output energy not input energy (which is what food calories - kCal indeed - are).

Before I used livestring and then myfitnesspal I tended to assume that 1kJ => 1kCal, i.e. canceling out the 4:1 division. This approximation assumes that the 4.2:1 ratio between a kCal and a kJ is roughly cancelled out by the inherent efficiency of about 25% in human energy matabolism. Hence the figure I would have used would be 2530kCal.

From wikipedia:

The efficiency of human muscle has been measured (in the context of rowing and cycling) at 18% to 26%. The efficiency is defined as the ratio of mechanical work output to the total metabolic cost, as can be calculated from oxygen consumption. This low efficiency is the result of about 40% efficiency of generating ATP from food energy, losses in converting energy from ATP into mechanical work inside the muscle, and mechanical losses inside the body. The latter two losses are dependent on the type of exercise and the type of muscle fibers being used (fast-twitch or slow-twitch). For an overal efficiency of 20 percent, one watt of mechanical power is equivalent to 4.3 kcal per hour. For example, a manufacturer of rowing equipment shows burned calories as four times the actual mechanical work, plus 300 kcal per hour,[17] which amounts to about 20 percent efficiency at 250 watts of mechanical output. The mechanical energy output of a cyclic contraction can depend upon many factors, including activation timing, muscle strain trajectory, and rates of force rise & decay. These can be synthesized experimentally using work loop analysis.

Note the 300kcal/hour constant used by Concept II on the rowing machine. I think you have to assume an increased energy burn from cycling over and above that purely attributable to mechanical power (e.g. it takes more effort to ride an electric bike than to lie in bed). I'm not sure how much we can attribute to that but it can't be zero so there must be some additional energy consumption above that ~2500kCal that I can't directly measure.

Thanks

[spenceey]

80.9 again this morning.

Slowly edging towards my target. Also private physio visit this weekend. Hopefully they'll sort my knee out, for now I've been resting Ice and compression.

Also borrowed an ultra scan machine (someone I work with brought one a while ago for Tennis Elbow) which I used last night for 5 minutes.


Knee feels slightly better today, pain is still there but hopefully a few more sessions like this and the physio on Saturday will have me right as rain.

[Wowbagger]

I find I forget from one week to the next how much I was last week. Checking this morning, I was 1.6kg down from last Wednesday's figure, which is much too fast given that I've been losing weight steadily since 1st Jan. No wonder I felt extra-hungry after breakfast! On the strength of that I allowed myself a couple of marmalade butties after my shredded wheat.

[Feline]

The eBay seller I bought my dynamo hub USB cable from has sabotaged my diet by including a box of German chocolates with my order!