The only diets that have been proven effective for long term weight loss focus on higher amounts of protein and vegetables, and limit carbohydrates to those that are harder to digest. Current government nutritional recommendations for a healthy diet are for 15% of your calories to come from protein, 35% from fat and 50% from carbs.
As part of the diet, you've been eating foods that you don't really like. You've also had to eat different meals compared to the rest of the family. You've kept away from chocolate even though you love it. And you've even managed to go to the gym a few times. Then you decide to weigh yourself. And shock, horror, you've only lost three pounds.
The underlying problem is that for women over 40, exercise ALONE is not enough to cause weight loss. This is not true for men. And it's less true for women under 40. But if you ask most women over 40, they will tell similar stories of exercise programmes that no longer delivered the goods when it came to weight loss.