Women over 40 have different metabolic needs, so you'll need to make some dietary adjustments just to stay the same weight. Here's the best diet approach

Fat may be higher in calories than carbohydrates or protein, but it satisfies your hunger—and that's key to keeping your calorie count down. People tend to lose more weight and keep it off on a calorie-reduced diet that contains healthy fats rather than a diet that's low in fat. That's why the best diet for women includes a source of healthy fat at each meal and snack. This could be two teaspoons of extra virgin olive oil, two tablespoons of raw nuts or seeds, or half an avocado.
Choosing the right fat is also key to staying healthy. Aging is associated with increased cholesterol, triglycerides, fat mass, and BMI. While fiber plays a part in reducing cholesterol levels, the types of fat you eat can also keep you healthy as you age. We're talking beautiful, glowing skin, shiny hair and more! The key is to focus on unsaturated fats, particularly anti-inflammatory omega-3s.
If you replace the saturated fats in your diet—think butter, red meat—with unsaturated fats, research suggests it can lower your cardiovascular risk, and omega-3s are especially known for their heart-healthy benefits. One study found that omega-3s are also helpful in stimulating muscle protein synthesis to preserve muscle mass as you age.
Seafood sources of omega-3s such as salmon, mackerel, tuna, and fish oil supplements provide forms of omega-3s known as EPA and DHA, the types that your body can use most easily (and the types with plenty of research backing). Plant sources like walnuts, flaxseeds, chia seeds, and hemp seeds provide ALA omega-3s. ALA must be converted to EPA and DHA in your body through a process that isn't super efficient, so plant-based sources should be supplemented with fish! Eating at least two servings of omega-3 rich fish every week covers you for your daily recommendation of 500-1,000 mg.