Overweight is OK, but if she's 300lbs there's a couple problems.
First, she is obviously unable to integrate fitness into her life. Whether it's laziness, or she's busy or whatever, I don't know. But if she doesn't have a desire to get more healthy, as the FUCKING HEALTH MINISTER, something's up. How can she make food and exercise suggestions that kids and adults can easily apply in their life? Why isn't she applying these suggestions to herself?
Second, she will likely go full fat-acceptance. Tell kids it's okay to weigh ten stone at 5 years old and such because she doesn't want to admit she would be considered obese and unhealthy by any reasonable standard.
Basically, her body tells us more about her attitude toward fitness than her resume. And it's an attitude I would hate for the entire country to adopt.