While the diet foods of each era inevitably fall out of fashion, could any of them be due a revival? 'Grapefruits can themselves be part of a healthy balanced diet, containing fibre and vitamins, but do not form a nutritionally complete diet on their own. 'Any weight loss will, again, result from the extreme calorie deficit rather than actual sustainable lifestyle changes and health benefits. 'Fewer calories over time can lead to weight loss, but at this extreme, it leads to nutrient deficiencies and other poor outcomes instead. 'Today's landscape looks different, and plenty of fat-free yoghurts can fit into a balanced, healthy diet.