Browse the evidence

Computed tomography (CT) assessment of muscle mass and myosteatosis lacks standardization across studies, with significant variation in anatomic landmarks, thresholding values, and reporting of technical parameters like contrast use and slice thickness.

When interpreting or conducting CT-based muscle assessments, ensure strict adherence to standardized protocols regarding anatomic landmarks (e.g., L3), thresholding values, and reporting of technical parameters (contrast, slice thickness). Lack of standardization currently limits the ability to compare results across studies or clinics.

Weight-loss and bodybuilding supplements, particularly those containing ephedra, DMAA, or adulterated with unlisted drugs (e.g., anabolic steroids, fluoxetine), carry a significant risk of severe adverse events including liver failure, cardiovascular collapse, and death.

Avoid weight-loss supplements containing ephedra, DMAA, or unlisted ingredients. Bodybuilding supplements are frequently adulterated with steroids or other drugs. If you experience liver symptoms (jaundice, fatigue) or cardiovascular issues (palpitations, chest pain) after taking these, stop immediately and seek medical help. The risk of severe injury or death is real.

Bone Mineral Density (BMD) is an imperfect predictor of fracture risk because it fails to account for bone size, geometry, quality, and turnover rates, leading to potential misinterpretation of intervention efficacy.

Do not rely solely on BMD (DXA scan) results to determine your fracture risk or the success of your treatment. Bone strength involves geometry, quality, and fall risk. Focus on overall bone health strategies (nutrition, exercise, fall prevention) rather than just trying to 'raise your number'.

Across all populations, antihypertensive medications achieve greater systolic blood pressure (SBP) reductions than structured exercise interventions, with a mean difference of -3.96 mmHg.

Structured exercise lowers blood pressure, but not as much as medication. If you have hypertension, do not rely on exercise alone to manage it; consult your doctor about medication. Exercise is a valuable adjunct, but medication provides a stronger effect.

Gene-by-environment interactions are the primary drivers of body weight regulation, and neither the set point nor settling point models fully explain obesity without considering these interactions.

Your weight is determined by how your specific genetics respond to your specific environment. You cannot change your genes, but you can change your environment. Effective weight management requires recognizing that what works for one person (genotype) in one environment may not work for another, and interventions must be tailored to this interaction.

Sarcopenia is defined by a combination of muscle weakness, low muscle mass, and impaired physical performance (e.g., slow walking speed), with prevalence ranging from 4% to 27% in older populations.

Sarcopenia isn't just 'getting old'; it's a specific condition defined by weakness, low muscle mass, and slow walking. Screening for these metrics can help identify at-risk individuals for early intervention.

Dietary intake measurements provide only a guide to, and not a direct measure of, the amounts of energy and nutrients available for metabolism.

Understand that dietary tracking is an estimate, not a precise measurement of what your body uses. Use it to identify trends and patterns rather than obsessing over the exact calorie or nutrient count, as food intake does not equal metabolic availability.

Natural experiments with weaker study designs (cross-sectional, case-only) are more likely to report positive associations with interventions than those with strong designs (longitudinal with comparison groups).

Be skeptical of positive findings from single-site, cross-sectional studies of policy changes. Prioritize longitudinal studies with comparison groups for evidence-based decision making.

High-protein diets are not recommended by the AHA because they restrict healthful foods, leading to nutrient deficiencies and potential long-term health risks.

Do not follow a high-protein diet that eliminates major food groups like fruits, vegetables, and grains. These foods provide essential nutrients and fiber. A balanced diet that creates a caloric deficit is safer and more sustainable.

Genetic factors account for 30-60% of the variance in cardiorespiratory fitness response to exercise training in humans.

Your genetic makeup determines a significant portion of how much your fitness will improve with exercise. This is not a failure of willpower. If one type of exercise doesn't work, try others, as genetic response to specific modalities may vary.

Comprehensive longitudinal monitoring of aging factors—including physical, psychological, and nutritional variables—is necessary to identify early markers of disease and determine reference values for normal aging.

To optimize long-term health, do not rely on a single metric. Regularly assess your physical function, nutritional intake, and psychological well-being. This holistic approach helps distinguish normal aging from disease onset, allowing for earlier intervention.

Current global food systems are failing to deliver high-quality diets, resulting in a triple burden of malnutrition (undernutrition, micronutrient deficiencies, and obesity) that represents the number one risk factor for global disease burden.

Your current food environment is actively working against your health by making unhealthy foods cheaper and more available than nutritious ones. Individual willpower is insufficient to overcome this systemic failure. To improve your diet, you must actively navigate these barriers by seeking out affordable nutrient-dense options (like pulses, vegetables, and animal-source foods where affordable) and advocating for policy changes that make healthy choices the default, rather than relying on the market to self-correct.

Current tobacco smoking modifies genetic susceptibility to obesity traits, specifically increasing genetic variance explained for overall adiposity (BMI) while attenuating genetic effects on body fat distribution (waist-to-hip ratio).

If you smoke, your genetic risk for gaining overall weight (BMI) may be higher than if you didn't smoke, but your genetic risk for storing fat around your waist (body shape) may be lower. Quitting smoking might change how your genes express themselves regarding weight distribution. This highlights that lifestyle choices like smoking can interact with your DNA to influence your body composition.

Dietary restriction extends lifespan in laboratory model species (yeast, nematodes, flies, rodents) by reducing both age-dependent and age-independent mortality rates, but this effect is significantly attenuated or absent in non-model species and males.

Dietary restriction can extend lifespan in model organisms, but the benefit is not universal. It appears stronger in females and specific lab-adapted species. For humans, the balance of protein to calories matters more than total calories alone. Do not assume lab results translate directly to wild-type human physiology without considering sex and genetic background.

Epigenetic aging, as measured by the Skin&blood clock, is distinct from cellular senescence, telomere attrition, and genomic instability, but is associated with nutrient sensing, mitochondrial activity, and stem cell composition.

Epigenetic age is not a simple proxy for cellular damage or telomere length. Interventions that extend lifespan (like caloric restriction or rapamycin) slow epigenetic aging, while those that extend lifespan via other mechanisms (like NAD precursors or metformin in this specific context) may not. To influence epigenetic age, focus on nutrient sensing (mTOR pathway) and mitochondrial health, as these are mechanistically linked to the clock's ticking, distinct from DNA repair or telomere maintenance.

Bariatric surgery induces significant lean body mass (LBM), fat-free mass (FFM), and skeletal muscle mass (SMM) loss, with approximately 55% of LBM loss occurring within the first 3 months post-surgery.

If you undergo bariatric surgery, expect to lose about 8 kg of lean body mass within the first year, with more than half of that loss happening in the first 3 months. This is not just fat loss; it includes muscle. To protect your metabolism and function, you must prioritize protein intake and resistance training immediately after surgery, not just focus on calorie restriction.

Genetic variants near KCNQ1, ALDH2/MYL2, ITIH4, and NT5C2 are significantly associated with Body Mass Index (BMI) in East Asian populations, explaining approximately 0.16% of BMI variation collectively.

This research highlights that specific genetic variants are linked to higher BMI in East Asian populations. However, these genetic factors explain a very small fraction (0.16%) of body weight differences. This means that while your genetics may contribute slightly to your weight, they are not the primary determinant. Lifestyle factors like diet and physical activity have a much larger impact on your BMI than these specific genes.

The association between BMI and specific genetic loci (KCNQ1, ALDH2, MYL2) is significantly stronger in men than in women within East Asian populations.

For East Asian individuals, genetic risk factors for BMI may manifest more strongly in men than in women. This suggests that genetic counseling or risk assessment might need to account for sex differences, although lifestyle interventions remain the primary tool for weight management for both sexes.

Consumer-grade wearable devices are not exempt from rigorous performance evaluation simply because they are marketed as 'research' or 'clinical' grade, as proprietary algorithms and hardware inconsistencies can still lead to significant errors.

Do not assume a device is accurate because it is 'clinical grade' or 'FDA cleared'. You must validate the specific device's sleep staging accuracy against PSG for your specific study population before using it for research conclusions.

When total training volume is equated, increasing resistance training frequency per muscle group (from 1 to 3+ days/week) does not significantly or meaningfully increase muscle hypertrophy.

If you want to maximize muscle growth, focus on getting your total weekly sets in. How you split those sets across the week (1 day vs. 3 days) does not matter for hypertrophy, provided the total volume is the same. You can train each muscle group once a week or multiple times a week; choose the schedule that allows you to recover well and stick to your program.

Lower socioeconomic status (higher Townsend Deprivation Index) significantly amplifies the genetic effect on BMI.

For those with high genetic risk for obesity, socioeconomic factors like deprivation can amplify the genetic effect on BMI. Addressing socioeconomic barriers may be as important as lifestyle changes in mitigating genetic risk.

Most commercially available consumer sleep monitors (e.g., Fitbit, Lark, Sleep Cycle) lack published validation studies comparing their sleep-wake metrics or smart-alarm features to gold-standard PSG or standard actigraphy.

Be skeptical of 'sleep quality' scores and 'smart alarms' from devices like Fitbit or Lark if they lack published validation. These devices often overestimate sleep time and misclassify stages. Use them for general trends (e.g., 'I sleep less when I drink alcohol') rather than precise medical data.

Patients with Obstructive Sleep Apnea (OSA) face a significantly increased risk of major perisurgical adverse outcomes and perioperative death when undergoing bariatric surgery.

Having sleep apnea makes weight loss surgery much more dangerous. It triples your risk of dying during the procedure. This is why doctors require a sleep study before surgery.

Tobacco smoking and high blood pressure are the leading preventable causes of death in the United States, responsible for approximately 467,000 and 395,000 deaths respectively in 2005.

Stop smoking and manage your blood pressure. These two factors alone account for roughly 20% of all adult deaths in the US. Effective interventions exist for both, making them the highest-impact targets for improving longevity and health.