One reason is that they likely have a mutation that deletes information from the POMC gene, which controls their ability to feel full.
It is interesting to note that this mutation makes them a popular breed to train as guide dogs because they are highly motivated by food. What is important to note here is that a loss of genetic information is actually beneficial to them as far as being trained to be a guide dog. This is not evolution though, it is De-evolution - a loss of genetic information. Even a loss of genetic information can produce traits that are seen as positive. These traits are in the minority however because must produce negative traits - such as becoming overweight.
So even labs are the victims of a fallen world as a result of sin against God as evidence by their degrading genome. Give your dog a big hug and know that God can restore their genome to perfection one day too.
Tour the links in the "More" section of this site to learn more about why evolution is not true and the observable science points towards a perfect original creation by God.
Click the image below to read a scientific article to support this statement.
I'm busy working on my blog posts. Watch this space!