The Queen Mother has defied the ravages of time
A scientist in Canada has been studying the ageing process for the past 10 years and found most people are 15 or more years older biologically than chronologically.
Dr David Wikenheiser said: "We all know people who are 30 but look over 40 and others who are 70, but look 50.
"The difference comes down to lifestyle. Some people's bodies get "rusty" faster than others and this makes them age more quickly.
"Virtually every ageing process is related to the oxidative compounds or free radicals produced by our body as a reaction to pollution, ultraviolet light, stress, smoking, alcohol and pesticides.
"But these can be neutralised by antioxidants."
Genetic inheritance
He points to people like the Queen Mother and Rolling Stones' guitarist Keith Richards, who are successfully defying the ageing process.
However, he suggests this may be influenced more by genetics than lifestyle.
A questionnaire he has devised calculates a person's true biological age and makes recommendations on how to lower it by a combination of healthier eating, exercise and stress management.
Dr Wikenheiser believes it is possible to lower your biological age by 10 years in three months with the right lifestyle changes.
He said: "You can't alter your genetics but you can make other changes, such as eating the right food, drinking enough water to flush out toxins, exercising and managing stress.
"We can take charge of our lives as individuals."
The questions include:
Brain strain
The charity organisation Research Into Ageing believes the questionnaire shows how important it is to take control of your lifestyle.
A spokeswoman said: "Ageing is a life long process and it's a good idea to think about how healthily you are doing it.
"More of us are having the opportunity to live into our 70s, 80s and beyond and research shows that it is never too late to make changes for the better.
"But we still need to fund research into what tends to go wrong as we get older and to discover how treatments can be improved so that more of us can have the active independent old ages we hope for."
Dr Wikenheiser stresses the importance of multivitamin and antioxidant supplements even if people are eating the right amounts of fruit and vegetables.
He said: "Today's soil tends to lack essential minerals so these are no longer found in the food we eat in large quantities."
He emphasises the need to eat three meals a day because missed meals put a strain on the brain as blood sugar levels drop.
Many of us are also eating the wrong fats or avoiding fat altogether, which deprives our bodies of important nutritional oils.
People should also ask their dentist what kind of fillings they have in their teeth.
"Amalgam fillings in your teeth are not stable and will contribute to toxic metal levels in your body," said Dr Wikenheiser.
The questionnaire is available in health food shops or by phoning 08450 606070 or by e-mailing: info@savant-health.com.