Weight loss is so individual, both in terms of the physiology and the psychology. I don't really think we have enough info about the OP's husband to make very specific recommendations.
If he is only 10-20 lbs overweight and already eats relatively healthfully, and if he does some exercise and has decent muscle mass, and if he doesn't tend to get ravenously hungry between meals or snacks (or have blood sugar crashes), then fasting might work quite well for him to drop a few pounds as long as he doesn't dramatically cut his calorie intake and send his body into 'starvation' mode, which can mess up metabolism longer term.
However, if he is considerably overweight, eats a lot of sugar and simple carbs, and does little exercise and has low muscle mass, then his insulin/glucose processing might be somewhat impaired. In that case, I suspect that suddenly starting intermittent fasting might mess him up metabolically by making his body think he's suddenly starving, or by causing hypoglycemia that causes him to function suboptimally or to overeat when he does eat.
My understanding is that fasting can improve insulin function in some people, but he might want to try other, less drastic methods that do the same thing first...such as the tried-and-true method of cutting sugar and simple carbs (high-glycemic foods) way, way down in the diet. Once insulin function improves, weight maintenance becomes easier.
Dramatic TEMPORARY changes to eating patterns usually don't work long term, and often result in regaining equal or more weight when they are discontinued. Whereas making manageable adjustments to eating that can stick permanently do often work. To some extent, this is a matter of his personality and psychology, as well as his particular body issues and goals.