Listener question on nutrition and weight loss

We received this question from Ryan Bates, a Fast Talk listener from Ann Arbor, Michigan. We spoke at length in episode 129 about this topic, but we also want to answer him here.

"Cyclists are often trying to lose weight to increase watts/kg.

I have read that cutting more than 500 calories per day from the total needed to maintain your current weight will actually slow down your metabolism, and make weight loss harder overall. Say, if you need 2000 calories per day, and cut down to less than 1500. Is this true?

If so, does it matter, for the purposes of potential slowing of your metabolism, if the deficit is produced by exercise versus calorie restriction? A few big ride days in a row can put you in a pretty big deficit.

If true, how many days of 500+ calorie deficit (approximately) are needed to trigger metabolism slowdown?

For context, I am 6’ 2", and have gotten myself down from 235 to 198 (thanks bikes!). I average 1500-1600 calories of intake per day, and exercise takes my daily net average down to 1100 calories per day. I am fueling more before races or long training sessions.

Thanks so much for your insight!"

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This is a great question. The short answer is, “not necessarily.” So the thing with nutrition is there’s a lot of thresholds and numbers that get thrown around. And this is what makes the nutrition piece of it so difficult is we need to really consider each individual person as this unique entity, and look at not only their intake, but then their expenditure as well. So potentially cutting more than 500 calories per day, could slow his metabolism depending on how much he’s exercising. I’ve seen athletes in the past where they’ve had very small deficits, maybe 200 calories 250, but they’re exercising so much that now that small deficit becomes a problem. If we look at the other side of it, where someone does a very severe caloric restriction and are only consuming around 1000-1200 calories, we start to get into these very low calorie diets. Then if they start to exercise or do a little bit too much exercise, now that becomes a problem, and they can see that affecting their metabolism.

In a case like this I always recommend trying to measure your metabolism. A quick Google search gave me a result of Fitnescity with a location in Ann Arbor that you might check out. They offer resting metabolic rate testing and have Dietitians on staff who would be able to interpret the results and break down the information so you can apply it to your situation.

I would recommend a baseline test to establish your needs and then you can easily track changes - e.g., see if your calorie deficit causes a significant reduction in resting metabolic rate results. For reference, anything less than 100-200 kcal/day is within the measurement error and I would not consider this a significant change.

I think this the key for me. I was a competitive cyclist from 1985 - 1995, quit cycling due to life changes (job and school) and became morbidly obese (went from about 155 to 285 over the next 18 years, June 2013 decided I needed to change my ways and dropped 100+ pound over the winter and returned to racing in 2014. Since then I’m in a constant battle to maintain my weight. Every few months I break out MyFitnessPal and start weighing everything that goes in my mouth and resetting portion sizes. While meeting my caloric targets based on general RMR charts has me still struggling to maintain weight.

I strongly believe that once you are morbidly obese (not that I believe the original poster of the question fits that profile based on the height and weights he provided), you have lowered your metabolic “setpoint” and as mentioned in this video clip (should be bookmarked at about 15min 40sec for the lead in examples of people not being able to maintain weight loss, then around 17 min discusses the “lowered setpoint”): it could be 20% lower than a person of the same weight, age, activity level. I haven’t found any other sources to back this up; maybe it’s been disputed?

I’ve been searching for a local facility to get my RMR tested but the ones that have done it in the past are either out of business or no longer doing the testing. My sports doc has given me a lead to a local college that may have testing capabilities but they aren’t doing it right now while we are in pandemic lockdown. :frowning:

You’re an inspiration Theo for determination and grit it must have taken to drop 100+ lbs. Hats off to you.


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I’ve been morbidly obese, over 314lbs, now I fluctuate around 230lbs, but it took me a couple of years to go down to around 220. How did you loose all that over the winter? I’d love to loose 30lbs over this winter :wink:


Congrats on your great weight loss!

I lost the bulk of my weight prior to getting the idea to get back into training for racing so I didn’t really fuel properly for workouts or fitness gains. My bulk weight loss came from an unsustainable diet for training. I did what I called a feast and famine diet. I alternated daily with <600 calories one day and eat whatever I wanted the next. The thought of no-restrictions tomorrow helped me get through the restricted calorie days. I also thought the variance in daily calories was enough to prevent my body from turning down my metabolism to match a chronic caloric deficit.

As the weight came off, I became more aware of my intake on the no-restriction days and focused on food quality. I could no longer maintain the feast/famine diet once I dropped the bulk of my weight and started to train (rather than just riding my bike to burn calories). During that time the off-limits list included items like: beer, peanut butter, most any spread or sauce you put on something else to make it taste better, after dinner snacks, and second helpings.

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Congrats to you too!

I know exactly what you mean about having a very restrictive diet and training, it is very hard and not sustainable. I did try intermittent fasting once but was seeing fat loss gains as in the restrictive diet, so I stopped.

I’ll go back into diet mode, been kind off this year, and try to loose more weight this winter since I doubt racing will return in spring most likely during summer, so I will have some time to ramp up the high intensity training mid-spring.

Thanks again for your reply :+1:t2: