Personally having a lab that is probably 25 lbs over weight with a healthy diet, this article provides the insight of why this could be happening
A new research shows that nearly 25 % of Labrador retrievers are missing a gene that helps control hunger.
The deletions take place in the POMC gene, which provides instructions to make a protein called proopiomelancortin, a protein which helps us feel full. Dogs with this mutation are about 2 kilograms heavier on average and are 10% more likely to beg for food and hunt for scarps according to a survey.
This finding mat explain why the Lab is the most obese dog breed with 60% fitting into this category.
The bright side to this is labs are the most popular guide dogs because food motivation makes them easy to train. Scientist looking into the guide dogs genes found more than three-quarters of them had a chunk missing from their POMC gene.
Next time your lab comes begging for food give them exercise not the extra fries.
http://www.sciencemag.org/news/2016/05/why-my-dog-fat-gene-deletion-may-provide-clues
