I could be dating myself here, but about 10 years ago when I was a gym owner and spent a lot of time training general population clients, there was an accepted principle that to calculate a persons’ caloric requirement for weight loss you simply had to multiply their bodyweight in pounds by 10 (or 10kCals per pound.) I’m not sure where this guideline came from, but you can still see it out there in the inter webs. This guideline served me well and many of the clients who adhered to this guideline had no trouble losing weight. However, I found that when working with athletes who generally had more muscle and were more active than the gen pop folks I was used to working with, it simply did not work. I quickly found that the majority of the time folks would lose weight too rapidly. Along with that rapid weight loss, strength and gym performance would go down the tube as well. It did not take me long to figure out I needed better methods.
This is one of the reasons I insist on having a pre-start data gathering period before writing any long term dieting program for athletes. Losing weight that quickly is simply not worth the strength and muscle loss that comes with it for us as strength and physique athletes. With 3 to 4 weeks of fairly accurate tracking of kCals and body weight, one can calculate the deficit or surplus during that period of time based on the rate of loss or gain in body weight. Then based on 3,500kCal roughly equaling one pound of body weight/fat, we simply add or subtract those calories back in. We here at 3DMJ have talked about this before many times in various formats. For example, let’s take a 150lb female who has tracked kCals and bodyweight for 3 weeks and lost 1.5lbs in those three weeks (that’s calculating average weight for the week by the way). We’ll make an arbitrary value of her mean daily average of caloric intake to be 2,000kCals during those 3 weeks.
- Starting body weight 150lbs
- Ending body weight 148.5lbs
- Average rate of body weight lost per week .5lbs (1.5lbs lost divided by 3 weeks)
- Weekly caloric deficit .5(lbs) x 3,500kcals = 1,750kCals
- Mean daily average 2,000kCals x 7 days in a week equals 14,000kCals
- 14,000kCals / week + 1,750kcal deficit during data collection = 15,750kCals per week
- 15,750kCals per week divided by 7 days = a mean daily average of 2,250kcals
So, for this female client to maintain 150lbs, the weight she was when she started data collection, she would need to eat a mean daily average of ~2,250kCals per day. This is pretty reliable as we collected the data that we made our calculations from while she was living her normal life, doing her training and with her current metabolic status. That being said any dramatic changes in lifestyle or physiology and the calculations would no longer be valid and the entire process would have to be done again for more accurate calculations.
Now this is where it gets fun. As any competitor knows, maintenance at one body weight is not maintenance at a different body weight. So, to help calculate maintenance calories at any body weight for this person, we’ve come up with a simplified “activity factor” that Alberto originally specified. So, like the old guideline of a taking a persons’ current body weight multiplied by 10 for weight loss, we will calculate an athlete’s “activity factor” to multiply any body weight for maintenance kCals. We’ll use our 150lb female athletes’ calculations.
- Maintenance kCals 2,250 divided by a body weight of 150lbs = 15.
What we have now is this athletes personalized “activity factor” or a value to calculate maintenance kCals at any body weight. Let say for example that this athlete lost 25lbs for a physique competition and ended at a body weight of 125lbs.
- 125 x 15 = 1,875kCals for Maintenance.
We could also use this value for planning gaining phases. For example let’s say the athlete wanted to gain 10lbs as part of her recovery diet. That would be a body weight of 135lbs.
- 135 x 15 = 2,025kCals to get to and maintain 135lbs.
As you can see, this is a very useful tool. However, it’s just a tool nonetheless. We as coaches and athletes have to know how to use the tools and principles available to us to not only derive accurate calculations, but also to individualize them to the diet program and the athlete. Indeed, not only does maintenance change at different body weights, sometimes the “activity factor” itself can change in dieted or non-dieted states for an individual, but you won’t know without experimentation. A good start is to use yourself as the guinea pig. Take your time to gather good accurate data and have fun calculating your personalized “activity factor”.