Cals in vs Cals Out

For the past 3 and a bit weeks I have been keeping a food diary, as accurately as possible, counting calories in vs  calories out. 

The results to date make interesting reading. 

I started at 71.1kg and my latest weight is 69.8 (measured last thing at night). So 1.3kg lost to date. Over this time I averaged a daily deficit of 764 calories. 

I am also measuring body fat% using some Tamita electronic scales. Now, while at least as if not more important compared to weight, this measure can be a bit hit and miss. It varies quite a lot during the day and day to day can shift quite a lot.

Still it's not entirely random and I think safest thing to check is a moving average over a week or so. This shows a reduction from 15.9% to 14.3%.

Taking the two sets of figures together 

• At start I weighed 71.1kg of which 15.9% = 11.3kg was fat
• Now I weight 69.8kg of which 14.3% = 10.0kg is fat

Difference = 1.3kg fat lost which matches weight lost. 

This is good news as it seems to indicate the weight gone is fat. One issue with diets is that you can easily lose a lot of weight (2-4kg) just by burning off glycogen. But this only takes a very small calorie deficit (2000kcal or so in total so can be done in a day) and comes back just as fast.

It's a bit of bad news though. In total my deficit is 18000kcal and this should mean more than 2kg of fat should have gone (assuming a pound of fat = somewhere between 2800 and 3700kcal (see here for source of these numbers))

It's possible I may be overestimating deficit but don't think so. I have been pretty assiduous in keeping the food diary for cals in and my cals out is based on power data which is pretty accurate.

This leaves one other variable which is base metabolic rate (BMR). I have set this quite low at 2300kcal, which is 200kcal less than the 2500 average for males that appears on all the nutrition advice panels on food.

But it looks as if this is still too high, by a factor of around 300kcal. 

This makes a sort of sense. It would account for my lifetime's fight vs the scales. It may also be linked (or even caused by?) my capacity to perform well in endurance events. 

Whatever, I will reduce my BMR to 2000kcal and see how that changes things.