Turning 40 is a major milestone—it’s a time to reflect on on career, family, and especially health. But let’s be honest: losing weight after 40 becomes significantly harder than it was in their 20s or 30s. Your metabolism isn’t as fast, muscle mass isn’t as easy to build, and energy levels fluctuate. Maybe you’ve tried cutting calories, hitting the treadmill, or skipping meals, only to see little progress. Sound familiar?The reality is, most men over 40 are making subtle mistakes that are undermining their weight loss. From relying too much on cardio to ignoring protein, small errors make losing fat and building muscle far more difficult than it has to be. The good news? It's never too late to correct your strategy. By making a few savvy adjustments, you can increase testosterone, create lean muscle, and regain energy. Here are five of the most important errors and how to correct them.1. Not Consume Enough ProteinOne of the largest myths concerning weight loss is that less is always better when it comes to food. Many men severely reduce calories, believing that the less they eat, the more weight they will lose. This, in most cases, translates to weight loss in muscle mass, not fat.Protein helps to keep muscle mass intact, particularly as men get older. It helps to repair muscle and maintain a greater metabolism, allowing weight loss to be more effective. The answer? Take one gram of protein per pound of your desired body weight per day. Use lean protein foods like chicken, fish, eggs, and dairy, and divide the intake into four to five meals a day. Without adequate protein, weight loss may equal muscle loss, and maintaining weight over the long term will be even more difficult.2. Doing too Much Cardio and Not Enough Strength TrainingMost men think the solution to dropping extra weight lies in cardio. The treadmill, stationary bike, and elliptical have been tied to losing belly fat for ages. But whereas cardio does hold some cardiovascular health benefits, it's not necessarily the best exercise for burning body fat.Too much cardio results in muscle loss, which decreases the rate of metabolism. Strength training, however, builds and maintains muscle, enhances metabolic rate, and maximizes fat-burning capacity even in resting conditions. A good fitness regimen must stress resistance training three times a week or more, along with incorporating moderate levels of cardio for cardiac health.3. Overlooking Stress and Sleep ManagementLife beyond the age of 40 tends to be accompanied by increased responsibilities—career expectations, family needs, and financial burdens. These stresses wreak havoc on the body, upsetting hormone levels and further complicating weight loss. Cortisol, the stress hormone, may result in excess fat storage, especially around the waist.In addition, inadequate sleep affects hunger and metabolism hormones, stimulating the desire for high-calorie, sweet foods. Men who are not well-rested have lower testosterone levels, which influence energy, muscle retention, and fat distribution. Getting adequate sleep—seven to nine hours nightly—can be a strong weight loss support. Meditation, deep breathing, and limiting screen time before bed can also keep stress levels in check.4. Failing to Adapt to a Changing MetabolismMetabolism slows down naturally with age, meaning that the approach that worked in your 20s may no longer be effective. A diet rich in refined carbs and unhealthy fats, paired with a lack of exercise, can lead to fat accumulation around the abdomen.To fight this, men above the age of 40 need to concentrate on complete, nutrient-rich foods. Decrease processed carbs, use healthy fats such as avocados and nuts, and boost fiber to control blood sugar levels. Intermittent fasting or eating smaller but more frequent meals can also work to control insulin sensitivity and for weight loss.5. Deficiency of Consistency and PatienceOne of the largest obstacles to effective weight loss after age 40 is inconsistency. Most men begin well with diet and exercise but soon give up when results do not happen overnight. Weight loss during your 40s is slower compared to earlier in your life, and development might be slower but more long term.Consistency is the key. Adhere to a planned workout regimen consisting of strength training and moderate cardiovascular exercise. Modify your diet in ways that you can sustain over the long term instead of using extreme fad diets.Don't count on old-school fitness strategies. Instead, make smart, long-term adjustments that promote both weight loss and overall health. With good sense and patience, getting fit after 40 is well within reach.