Being slim is often used as a marker of health and fitness. But researchers this week poured scorn on this idea, warning that a quarter of middle-aged women in the UK who are obese, according to their BMI, are actually fit. Researchers said this group, along with 10 per cent of obese men in Britain, fall into the 'fit but fat' category — meaning they don't have any weight-related conditions. A wave of overweight fitness influencers have long spread the word that being larger doesn't stop you...