Crash dieting has been associated with the devastating condition known as Telogen effluvium. In these circumstances you may lose more than 50% of your natural hair even if it is not directly related to male pattern baldness. The lack of protein and an increase in the stress response hormones will have these effects.
In conclusion you have to ensure that your diet program is slow but steady. Set targets that are achievable and yet you also have to ensure that there is enough challenge in the programs that are suggested within the guidelines. Rushing these things is not worth the hassle that you could eventually have to deal with.