I found on the internet this subject, for ex. obesity information. Weight loss diets can be causes for obesity? What do you think? My wife is in a weight loss diet program and now I am worried about her.
No weight loss diet can cause obesity. Yo-yo-ing on a diet if you are overweight (ex: dieting and then gorging and gaining the weight back) can make you gain more weight than you started off with... but that means the obesity is caused by lack of will power - not the diet itself.
It is not healthy to be obese. That being said, you cannot base obesity on BMI alone. Other things must be taken into consideration (such as skin fold measurements and exercise stress tests - all of which can be provided by a nutritionist, public health expert, or doctor). If you are solid muscle, there is a chance you might be considered overweight because muscle weighs more than fat. The number of people who actually have this problem, though, is low.
If your wife is overweight, then being on a weight loss diet is not bad for her and you should be encouraging her to continue the good work. If your wife is underweight and solid muscle, then she should not have to do a weight loss diet and may have a problem with control (like what is seen in anorexia neurvosa). Either way it's best to see your doctor before any weight loss program is commenced.