This is one of those times when a little information can be a dangerous thing.
Properly planned cheat meals can sometimes be used as part of a long-term fat loss plan to manipulate hormone levels, metabolism, etc. Full-on cheat days are relatively less common but, again, might be worked into a 12, 16, or 20+ week fat loss phase depending on progress.
A VLCD is a short-term plan by design, entirely setup to get results with drastic calorie reduction before the body catches on and those hormone/metabolism manipulations are necessary. Have one or two cheat days per week when you’re doing a four week plan means you’re only really sticking to the diet about 80% of the time. That’s obviously going to lead to subpar results.
Super-low calories combined with a ton of exercise is a very bad plan. This explains why: