ShapeFit.com has a list of factors that influence your BMR.
Basal metabolic rate, or BMR, is the minimum calorific requirement needed to sustain life in a resting individual. It can be looked at as being the amount of energy (measured in calories) expended by the body to remain in bed asleep all day! Calories are burned by bodily processes such as respiration, the pumping of blood around the body and maintenance of body temperature. Obviously the body will burn more calories on top of those burned due to BMR.
- Genetics: some of us are lucky, some of us aint
- Gender: men on average have more muscle mass and less fat
- Age: BMR drops with ~2%/10 years
- Weight: obese women can have a 25% higher metabolic rate than thin women
- Body fat percentage: if its low your BMR is probably high
- Diet: starving yourself puts your body in a reduced BMR-mode
- Body temperature: +0.5C = +7% BMR
- External temperature: ironically being cold also helps boosting your BMR
- Glands: Thyroxin helps regulate your BMR
- Exercise: lean tissue requires a higher BMR than fat tissue
So as you can see, it's not as simple as just looking at how 'fit' you've become to judge what your BMR will do. However, assuming you've lost some weight, reduced your fat level, aren't on a starvation diet and have acquired more lean tissue, you'll probably have a net increase in BMR.
If you look at the calculations:
- Men: BMR = 66 + (13.7 X wt in kg) + (5 X ht in cm) - (6.8 X age in years)
- Women: BMR = 655 + (9.6 X wt in kg) + (1.8 X ht in cm) - (4.7 X age in years)
And the activity multipliers:
- Sedentary = BMR X 1.2 (little or no exercise, desk job)
- Lightly active = BMR X 1.375 (light exercise/sports 1-3 days/wk)
- Mod. active = BMR X 1.55 (moderate exercise/sports 3-5 days/wk)
- Very active = BMR X 1.725 (hard exercise/sports 6-7 days/wk)
- Extr. Active = BMR X 1.9 (hard daily exercise/sports & physical job or 2X day training, i.e marathon, contest etc.)
You can see that increasing your activity level will boost your BMR with ~15-20%, whereas a loss in kilograms will lower it with 10-15 points per kilogram. So estimating what the effect will be:
- (66 + (13.7 * 87) + (5 * 176) - (6.8 * 26)) * 1.2 = 2353 (being sedentary)
- (66 + (13.7 * 82) + (5 * 176) - (6.8 * 26)) * 1.2 = 2271 (-70, slimmer but still sedentary)
- (66 + (13.7 * 82) + (5 * 176) - (6.8 * 26)) * 1.4 = 2649 (+300 slimmer but more active)
As you can see, being more active is most definitely going to increase your BMR. Even if you significantly loose weight, the difference is going to be quite significant. Not that this equation doesn't take into account all of the factors they listed themselves, but still you get the point.
So no, being more active is most definitely going to increase your BMR.