1yo female lab in heat w/ weight loss

Question
Hello, I am watching a dog for a fellow soldier while him and his family are away for the holidays.  She came in to heat and has been for about a week, and now she seems to have lost weight.  She is still acting normal, but i dont know if this is normal.  Any ideas?

Answer
I don't see how being in heat would do that but dogs that are not spayed tend to fluctuate in their weight anyway.
She may just look more sunken in around the 'waist' area because she is in heat-but unless you can weigh her and know the difference it is hard to say.
It could be that just being in heat burns up more calories.

She is coming into the bleeding part of her heat next (day 7-14) then she will be really ready to breed(day 15-18)-so unless you have a stud lined up for her keep her locked up inside. Many dogs have been bred through the fence that was supposedly protecting them from the roaming dogs!
The entire estrus cycle runs 21 days.

If you think she has lost over 5 lbs then just give her some more food to help her recover those calories. If she is very active that will increase her calorie burn on top of the estrus.
I hope this helps some!