Browse the evidence

Testosterone replacement therapy (TRT) reliably improves global sexual function (libido, erectile function, sexual satisfaction) in men with functional hypogonadism in the short term.

If you are an older man with confirmed low testosterone and sexual issues (low libido, erectile dysfunction), TRT (specifically starting with transdermal gel) is the recommended treatment to improve sexual function. However, you must be screened for prostate health first. Do not expect TRT to fix weight, diabetes, or bone density issues. If you want children, do not take TRT; ask about gonadotrophin therapy instead.

Chronic insufficient sleep duration is causally associated with adverse health outcomes including obesity, type 2 diabetes, hypertension, cardiovascular disease, and all-cause mortality.

Prioritize getting enough sleep to avoid the high risks of chronic disease. If you are consistently sleeping less than recommended for your age group, you are increasing your risk for obesity, diabetes, and heart disease. Treat sleep with the same seriousness as your diet and exercise.

Short sleep duration (less than 6 hours per night) measured objectively via actigraphy significantly increases susceptibility to developing a clinical common cold following viral exposure.

To lower your risk of catching a cold, prioritize getting more than 7 hours of sleep per night. This study shows that sleeping less than 6 hours significantly increases your odds of getting sick after exposure to the virus. Focus on total duration rather than just sleep quality or fragmentation.

Adherence to a composite healthy lifestyle index (HLI) comprising non-smoking, moderate alcohol intake, physical activity, normal BMI, and Mediterranean diet adherence is strongly inversely associated with the risk of developing cancer-cardiometabolic multimorbidity (subsequent occurrence of cancer, cardiovascular disease, or type 2 diabetes).

Adopt a composite healthy lifestyle to significantly lower your risk of developing multiple chronic diseases (cancer, heart disease, diabetes). This involves maintaining a healthy weight (BMI 22-23.9), not smoking, engaging in regular physical activity, limiting alcohol intake (0-12g/day), and following a Mediterranean-style diet. The study shows that even after developing one of these conditions, maintaining these habits reduces the risk of developing a second one by approximately 15-25% compared to unhealthy lifestyles.

Long-term detraining (30-32 weeks) in previously strength-trained women retains a significant portion of maximal dynamic strength and muscle fiber cross-sectional area, preventing a full return to pre-training baseline levels.

If you are a trained woman who must take a break from lifting for 30+ weeks, do not panic about losing everything. Your body retains significant strength and muscle structure. When you return to training, you will regain your previous fitness levels much faster than an untrained person would, because your neural and structural adaptations are partially preserved.

Retraining after long-term detraining (30-32 weeks) induces rapid hypertrophy of fast-twitch muscle fibers (Type IIa and IIab+IIb) and a shift in fiber type composition from IIb to IIa, occurring faster than in untrained individuals.

When returning to lifting after a long break, your fast-twitch muscle fibers will grow quickly, and your muscle fibers will shift towards more oxidative (IIa) profiles. This structural change happens rapidly, contributing to the speed at which you regain strength.

For South Asian, Chinese, and Black populations, the BMI threshold associated with equivalent diabetes risk is significantly lower (24-26 kg/m²) than the standard 30 kg/m² cutoff used for White populations.

If you are South Asian, Chinese, or Black, do not wait until you reach a BMI of 30 to worry about diabetes. Your risk increases at lower weights (24-26 kg/m²). You should undergo diabetes screening and adopt preventive lifestyle measures at these lower BMI thresholds, as your body may store fat in ways that increase metabolic risk more efficiently than in White populations.

Increased intake of EPA and DHA lowers the risk of coronary heart disease and cardiovascular mortality, primarily through the modification of risk factors such as triglycerides, blood pressure, and inflammation, as well as through anti-arrhythmic and anti-thrombotic mechanisms.

To support heart health, aim for higher intakes of EPA and DHA, ideally through fatty fish consumption or supplements. This is associated with lower risks of coronary heart disease and cardiovascular mortality. Key benefits include lowering triglycerides, blood pressure, and inflammation. While recent studies have been mixed, the overall body of evidence supports a protective role, especially for secondary prevention in those with existing heart disease.

High dietary calcium intake (approx 1,000 mg/day) reduces adiposity and accelerates fat loss by suppressing 1,25-dihydroxyvitamin D, which lowers intracellular calcium in adipocytes, thereby inhibiting lipogenesis and stimulating lipolysis.

To support fat loss, aim for approximately 1,000 mg of calcium daily, preferably from dairy sources like yogurt or milk, rather than supplements. This helps regulate hormones that control fat storage and breakdown. If you are restricting calories, this high calcium intake will accelerate fat loss compared to low calcium intake.

Adequate intake of long-chain n-3 PUFAs (DHA/EPA) during pregnancy and lactation is critical for the normal neurological development and cognitive function of the infant.

Pregnant and breastfeeding women should ensure adequate intake of long-chain n-3 PUFAs (DHA/EPA) through diet (e.g., oil-rich fish) to support baby's brain development, while being mindful of mercury limits.

Non-exercise activity thermogenesis (NEAT), defined as the energy cost of spontaneous physical activity, fidgeting, and posture maintenance, constitutes the most variable component of total daily energy expenditure and accounts for the remainder of energy needs after basal metabolic rate and thermic effect of food.

Focus on increasing your daily spontaneous movement (NEAT) like fidgeting, standing, and walking, as this variable component often outweighs structured exercise in total calorie burn for sedentary individuals. You do not need to exercise to significantly impact your daily energy expenditure.

Persistent physical inactivity during adolescence (ages 16-18) strongly and independently predicts the development of adult obesity and abdominal obesity by age 25, establishing a causal link between early sedentary behavior and later adiposity.

If you are a teenager or young adult, staying physically active is one of the most powerful things you can do to prevent obesity later in life. It doesn't matter if your parents are overweight; your activity level during your teens is a stronger predictor of your adult weight than your genes. Start moving now to break the cycle of inactivity and weight gain.

Once obesity is established, it creates a self-perpetuating vicious circle where obese individuals exhibit significantly lower physical activity levels and avoid high-intensity exercise, leading to lower total energy expenditure relative to body mass despite higher basal metabolic rates.

If you are overweight, you likely move less than you realize, which keeps your total calorie burn lower than expected. You don't need to run marathons; simply increasing your daily movement (steps, standing, light activity) can significantly boost your energy expenditure and help break the cycle of weight gain.

Abdominal obesity is more strongly predicted by adolescent physical inactivity than overall obesity, and self-perceived poor fitness in adolescence is a significant independent risk factor for adult abdominal obesity.

Don't just look at the scale. If you were inactive as a teenager, you are at high risk for abdominal fat, which is dangerous for your health. You can mitigate this risk by staying active. Measuring your waist circumference is just as important as your weight.

When eccentric and concentric resistance training are matched for maximum load or total work, they produce similar increases in whole muscle size (hypertrophy), despite inducing distinct structural adaptations.

If your goal is maximum muscle size, you do not need to prioritize eccentric-only training. As long as you match the total work or the load used in concentric training, eccentric training will build similar muscle mass. However, expect different structural changes: eccentric training tends to increase fascicle length (muscle belly length), while concentric training tends to increase pennation angle (fiber packing density). For general hypertrophy, either mode works if the stimulus is matched.

Eccentric resistance training primarily increases muscle fascicle length (serial sarcomere addition), whereas concentric resistance training primarily increases pennation angle (parallel sarcomere addition).

To optimize specific functional goals, consider the structural changes: eccentric training lengthens the muscle fibers (fascicles), which may improve range of motion and force at longer lengths. Concentric training packs fibers more densely (pennation), which may improve force production at shorter lengths. For general aesthetics, either works, but for sport-specific range of motion, eccentric emphasis might be beneficial.

Vitamin D supplementation reduces the incidence of acute respiratory tract infections, with the effect being more significant in patients with severe vitamin D deficiency (<10 ng/mL).

Taking vitamin D supplements can help reduce the risk of getting acute respiratory infections. This benefit is strongest if you currently have severe vitamin D deficiency. If your levels are normal, the benefit may be smaller.

Consumption of phytosterol esters (approx. 1.84 g/day) lowers plasma total and LDL cholesterol more effectively than phytostanol esters at the same dose, primarily by suppressing cholesterol absorption.

To lower cholesterol, choose margarines or spreads enriched with phytosterol esters over those with phytostanol esters. Aim for a daily intake of approximately 1.8-2 grams of free sterol content, typically achieved by consuming 2-3 servings of the fortified product daily. This intervention is most effective for individuals with elevated cholesterol levels.

Daily administration of the selective androgen receptor modulator GTx-024 (enobosarm) at 3 mg significantly increases total lean body mass and improves physical function in healthy elderly men and postmenopausal women without causing adverse androgenic side effects.

For healthy older adults looking to build muscle, a daily 3mg dose of the SARM GTx-024 (enobosarm) taken for 12 weeks significantly increases lean body mass and physical function without the typical side effects of testosterone therapy. This intervention works best when combined with maintaining your current diet and exercise habits, as the drug itself drives the anabolic response.

Daily administration of GTx-024 (enobosarm) at 3 mg significantly reduces insulin resistance and fasting glucose levels in healthy elderly men and postmenopausal women.

For healthy older adults, a daily 3mg dose of GTx-024 (enobosarm) taken for 12 weeks significantly reduces insulin resistance and fasting glucose levels. This metabolic benefit is comparable to standard diabetes medications like metformin, suggesting potential utility for metabolic health in aging populations.

Integrating sleep, sedentary behavior, light-intensity physical activity (LIPA), and moderate-to-vigorous physical activity (MVPA) into a unified 24-hour activity cycle (24-HAC) provides a more accurate assessment of health outcomes than evaluating these activities in isolation, as time spent in one activity directly displaces time in others and creates physiological synergies.

Stop viewing exercise in a vacuum. Your health is determined by how you spend all 24 hours. Prioritize getting 7+ hours of sleep, as this is the foundation. Then, look at your waking hours: minimize prolonged sitting by standing or moving lightly (LIPA) frequently, and aim for 150 minutes of moderate-to-vigorous activity per week. Recognize that moving more during the day can help you sleep better, and sleeping better gives you the energy to move more.

Low muscle strength (dynapenia) is independently and significantly associated with increased all-cause mortality in older adults, whereas low muscle mass (sarcopenia) alone is not significantly associated with mortality unless accompanied by low muscle strength.

For adults over 50, prioritize building and maintaining muscle strength (e.g., through resistance training) over simply focusing on muscle size or weight. Low strength is a strong independent predictor of early death, whereas having low muscle mass is not a significant risk factor if your strength remains normal. Measure your functional capacity, not just your body composition.

Primary care behavioral counseling interventions targeting diet and physical activity produce small, statistically significant improvements in intermediate cardiovascular risk factors (blood pressure, cholesterol, BMI) in adults without known CVD risk factors, but do not consistently improve long-term health outcomes like mortality or morbidity.

If you are generally healthy, talking to your doctor about diet and exercise will likely lower your blood pressure and cholesterol slightly. However, do not expect this counseling alone to prevent heart attacks or death. The benefits are modest and require sustained effort (high-intensity counseling yields better results).

EPA reduces cardiovascular risk through multiple mechanisms including lowering triglycerides, reducing inflammation, stabilizing cell membranes, and improving endothelial function, distinct from DHA.

EPA works by lowering triglycerides, reducing inflammation, and stabilizing cell membranes, which together protect the heart.