Although Mrs Mitchell has lived in Britain for more than 30 years, no one had told her how important her weight was to her medical condition until, in 1993, with the help and encouragement of a new GP, she lost four stone.
Now, she continues to slip into size 12 clothes and, with her blood pressure at normal levels, no longer has to take tablets to keep her weight down.
Even more pleasing to her is her first grandson, Jordan, now eight months - although he shouldn't be: he was born four months prematurely, weighing only 1lb 6oz. He is a miracle baby, Mrs Mitchell says.
Her youngest daughter, who is 16, has a heart murmur - "We just have to keep an eye on her." Because of high blood pressure, Mrs Mitchell spent the last five months of that pregnancy in hospital.
Mrs Mitchell is justifaibley pleased with her own achievement. She says: "I eat no meat, I don't eat bread or bananas, I use skimmed milk, I eat no butter, I eat lots of vegetables and fruit and I eat steamed fish seven days a week. I do it with nice seasonings, some salt, sweet peppers, a little honey and some garlic.
"I used to shops at Evans [specialists in large sizes] - now they don't have clothes small enough to fit me."
Her doctor at the Lewisham Triangle Surgery, south London, is Ngozi Uduku, who says: "It is true to say that people in ethnic-minority groups tend to have less understanding of how lifestyles can affect their health.
"There are a number of reasons for this. Many GP studies have shown that patients from the same social backgrounds as their doctors tend to be given more information. Where the social background is different, conversations tend to be short. People just get told the basics.
"You must look at both sides of this picture. People come with different cultural beliefs. There may be embarrassment and different views about when to see a doctor.
"A doctor can be seen as someone only for acute illness, for operations. We tend to see people first at a later stage of their illness."
Before Mrs Mitchell went to her new doctor she had been taking Valium, to make her calmer in the hope of reducing her blood pressure, as well as blood-pressure pills.
"But my blood pressure kept on going up," she recalls. "I try to eat healthily now. No one gave me any reasons why before."