In fact the main reason people fail diets like this is because they feel hungry, deprived of the foods they love, as well as feeling fatigued and tired. Most sports replacement shakes and formulated meal supplements on the market are usually too high in calories and often higher in sugar without enough fibre and protein – so you end up feeling hungry and craving sweet or sugary treats. But the 5:2 Diet Shake has helped changed this for many people - helping them get through the 2 fast days feeling more satisfied.