Do I need to compensate for calories spent exercising on a day to day basis?

Question

I have recently started getting into shape, mainly by counting calories at MyFitnessPal and getting more serious about my road cycling hobby. I'm in my late twenties and otherwise relatively fit, but need to lose about 25kg to reach my ideal weight.

Because I have so much weight to lose, I've aimed for quite agressive goal of 1kg per week. MyFitnessPal tells me I should eat 1000kcal below my calorie consumption daily. On a day when I don't exercise this means 1540kcal, but as I excercise more I get to eat more, and end up eating anywhere between 1500 and 2500 kcal on most days, thus compensating for the spent calories and hovering around the 1000kcal net deficit, +/-200kcal or so. This works fine for me and I am losing weight.

But then there is the odd day when I either go for a longer endurance ride, or I miss a meal for some reason, and my net calorie deficit can drop drastically. For instance today I cycled for 4 hours at an average speed of 27km/h. MyFitnessPal tells me that at my weight, 4 hours of "vigorous" cycling spends 4000 calories, but that sounds to high to me, so I opt for the lower category of "moderate" which gives me 3200. Add to that my 1540 base calories and that means I should eat 4740kcal today.

So far I've managed about 3000 (breakfast, lunch, dinner plus carb loading during the ride) and I feel perfectly fine. Am I really supposed to go ahead and make myself eat 1740 more?

This happens to me on average once a week. On the other hand, once I week I have a "cheat day" when I might go to the pub and eat at a restaurant, which puts me well over that day's calorie limit.

Am I hurting my weight loss by not sticking to my minimum intake on a day to day basis? Am I hurting myself? Or does it all even out in the long run?

There is a lot of mixed information about this online ("starvation mode", lowered metabolism, losing muscle, etc.), but I can't find anything that's based on any reliable sources.

Answer 1

Its not necessary to compensate for engery expended during exercise and can lead to eating too much to compensate. Measuring the energy expended during exercise varies wildly, and is never precise.

Instead, I'd recommend aiming for a lower weight loss per week and thus lower deficit per day, and exercising as normal. Aiming for a more conservating 0.5kg per week based on calroic deficit, and then exercising on top will get you to your goals just as quick, and will mean you have one less thing to measure.

With regards to "starvation mode" as @JohnP said, it is a myth based on the Minnesota Starvation Experiment, that was performed on already underweight people who were performing strenuous activity. The results were never shown to be applicable to the general public.