Or maybe your doctor or registered dietitian recommended an intermittent fasting plan for your health goals and you’re wondering if it’s OK to strength train—even if your last meal was 12 hours ago. Some people view peptides as a more natural alternative to anabolic steroids, praising them for their ability to boost muscle mass, promote fat loss, and help bodybuilders maximize their workout results. Several studies showed that a high-protein diet actually decreased testosterone levels. "You should exercise to keep your endurance, lean muscle, and low body fat, which will, in turn, keep you healthy," El-Zawahry says. For example, research has found that men who performed resistance training several times per week experienced increases in testosterone immediately after workouts and improvements over time. Over time, consistent resistance training also supports muscle growth and strength gains. But with research mounting on the benefits of resistance training, experts say a few things need to change at the gym to make it more enticing to women. One 2016 study found that men who followed an eight-week weight training plan while fasting for 16 hours a day lost some body fat, but didn’t gain any strength. Fasted strength training also tends to prompt the body to rely more on fat than carbs—similar to fasted cardio—so the strategy may help with body composition if fat loss is your goal, some research shows. If you’re serious about optimizing your testosterone levels, weightlifting should be a central part of your exercise routine. Cardio can enhance cardiovascular health, but it won’t do much for muscle growth, strength, or testosterone production. While cardio is excellent for cardiovascular health and burning calories, it’s weightlifting that truly stands out when it comes to enhancing testosterone production. However, working out alone won’t cause a long-term increase in testosterone levels, El-Zawahry says. By exercising, you’ll likely maintain a healthy weight and improve your cardiovascular functioning, which has positive effects on your testosterone. When you think of the gym, you think about people that are already more fit. During her first year of college, Elisabeth Bradley was inspired to try weightlifting after she followed a woman tracking her fitness transformation on social media, one barbell at a time. "If you’re fasting with the goal of losing fat but gaining muscle, that’s not going to happen," Horowitz says. When it’s best to eat (or not eat) in relation to exercise remains up for debate. "The trade-off though is that you also are at risk for less muscle protein synthesis." I would say people who are fasting should strength train," Horowitz adds. The best types of exercise to increase your testosterone levels are weightlifting and high-intensity interval training (HIIT). Consuming healthy fats may also help support testosterone levels and hormone balance. Eating enough protein can help you maintain healthy testosterone levels and can aid in fat loss, which may be beneficial, too. "So prolonged periods of fasting in general are probably not ideal if your goal is to build muscle mass to bulk up." "You're not going to have the right energy and you're going to actually potentially break down your muscle mass, because that's where the energy stores are going to come from," Dr. Butts says. If your lack of fueling makes you feel shaky during training sessions, you’ll likely miss some of your reps—or worse, suffer an injury. Athletes looking to boost strength aren’t going to have much luck going about their workouts fasted. There are real downsides to weight-lifting with no fuel in the tank. "If you're in an acutely fasted state, you're potentially in a better fat-burning state," Dr. Butts says. Told for years that being skinny is the ultimate goal, some falsely believe strength training will make them look bulky. There’s also still a stigma about women lifting weights, Bradley said. And so it feels like I have to make myself fit into this mold before I can feel comfortable being in a gym setting working out in front of other people," she said. One study following men with obesity found that regular exercise increased testosterone levels more directly than weight loss alone.16 Excessive cardio, especially long-duration endurance training, can even have a negative effect on testosterone levels by increasing cortisol—a stress hormone that suppresses testosterone production. This happens because your muscles undergo stress during resistance training, prompting your body to repair and strengthen them.
