Working in a personal training studio made me come across quite a few people who have weight concerns. Only a minority of clients wants to bulk up, whereas the majority wants to lose weight and some clients insist that they want to lose weight in very specific areas of the body. Unfortunately, targeted weight loss is unrealistic. It would take some form of genetic engineering and/or extreme hormone manipulation to achieve that.
Weight loss is organic and the body will get rid of fat through a combination of increased calorie expenditure (exercise) and a lower calorie intake. The end result is all-over weight loss. Your body's chemical composition will dictate your rate of fat loss; when you deflate a balloon, it will shrink in volume as a whole and not in parts.
Genetically, women's bodies will have more weight distributed in the bust, thighs and hips. Dramatic weight loss will affect the whole body and not just the areas just mentioned. Sudden and prolonged weight loss will severely affect hormone production which is linked to body fat percentage. Anorexia can in fact cause a woman's menstrual cycles to stop (unfortunately many female professional dancers and athletes are affected by amenorrhoea or lack of periods).
Stress can be one of the causes of weight gain. According to WebMD, the stress hormone cortisol can make us crave more food and stops us from feeling full after a meal. In extreme cases of cortisol over-production, people can develop Cushing Syndrome which causes weight gain in the upper body (especially the face, neck and shoulders). Lack of sleep is also often to blame, whether related to stress or induced by other factors.
The thyroid is accused of triggering weight gain when it is underperforming, however the thyroid is often used as an excuse for weight gain. Most people have a perfectly normal thyroid function.
During the menopause, women may tend to start accumulating more fat around the waist rather than their hips due to hormonal changes and Polycystic Ovarian Syndrome can also cause weight gain around the middle.
The only way to keep a healthy weight is to follow the body's natural rhythms. Anything forced or artificial (like working night shifts, getting greasy takeaways after a night out, working overtime or skipping meals) can make you hold on to body fat, even if you go to the gym and eat a healthy diet during the week.