
Sometimes the medicines you're taking for other issues, such as high blood pressure and antidepressant meds, can increase your weight or keep you from losing it, says Dr. Stanford. Ask your doctor if your weight concerns could be side effects of the prescriptions you're getting filled. Often, there are other formulations that can be effective but wouldn't have those side effects for you.
If you prefer a specific plan with specific rules, make sure it goes with your lifestyle, which, for most guys, gets increasingly complicated in your 40s with more responsibilities at work, with your family, and maybe even with your aging parents. A vegan diet can be hard to do in a healthy way if you live a grab-and-go existence. Meal prep is going to be a challenge if you’re never home long enough to cook. Don’t just pick what worked for a friend; pick what’s likely to work with your busy, over-40 lifestyle.
Alcohol adds unnecessary calories and sugar to your diet. Drinking alcohol may also increase your appetite, leading you to consume more calories.30 When you’re under the influence of alcohol, you may also be tempted to choose less nutritious options, such as processed junk foods. I recommend reducing your alcohol consumption to an occasional glass of wine or eliminating it completely.
"One of the reasons that it's difficult to lose weight in your 40s is that you are beginning to lose muscle mass, so the composition of your body tissue changes," explains Keri Peterson, MD, Women's Health advisor. "Having higher muscle mass raises your metabolism, so your body burns more calories." So when you're dealing with the opposite—less muscle mass—that means a slower metabolism. Argh.

In your forties, your body may have an increasingly difficult time digesting carbohydrates, which may lead to weight gain. Living a stressful life can lead to an increase in the stress-hormone called cortisol, which can make you more prone to gaining belly fat. Estrogen loss may also lead to fat redistribution in your body and cause belly fat gain.11

