I might suggest making smaller goals. Like 10 pounds by Christmas. Then, 10 pounds by Valentines Day. Or, a "no fast food except lunch on Saturday" rule or some rule that doesn't deny enjoyment, but that does control the amount. Also, unless he just needs to lose weight to meet some temporary goal like a fitness test or health insurance, liquid diets without changing life long eating habits don't tend to have lasting effects.

For my husband - I just remind him about all the negative sexual side effects of obesity and he gets back to healthy eating and exercising.

Good luck to you both.