The word you're looking for is "lose", not "loose". In the short term, they'd absolutely lose weight. After a certain point (probably about six weeks), their b

The word you're looking for is "lose", not "loose". In the short term, they'd absolutely lose weight. After a certain point (probably about six weeks), their basal metabolic rate will drop though, in adaptation to the new situation where their body adapts to living off a lowered caloric intake. Then the weight loss will plateau, or at least significantly slow down, while any deviation from the diet would generally result in a sharp uptake in fat storage (because now the metabolism is significantly slower and more greedy)