Browse the evidence

Aerobic exercise (AE) reduces intrahepatic lipid and visceral adipose tissue and improves insulin sensitivity in obese adolescent girls, whereas resistance exercise (RE) does not produce these specific metabolic benefits despite reducing intermuscular adipose tissue.

For obese adolescent girls aiming to improve metabolic health (specifically liver fat and insulin sensitivity) without losing weight, 3 hours of moderate-to-vigorous aerobic exercise per week (e.g., treadmill/elliptical) is effective. Resistance training alone, while beneficial for muscle strength and intermuscular fat, does not significantly reduce liver or visceral fat in this group.

In post-obese women, long-term weight regain is not predicted by metabolic abnormalities (resting energy expenditure, thermic effect of food, or fuel utilization) but is significantly associated with self-reported physical inactivity.

If you have lost weight and are worried about regaining it, do not assume your metabolism is permanently damaged. This study of post-obese women found that their metabolic rates were normal compared to those who never were obese. Instead, focus on maintaining physical activity levels, as inactivity was the strongest predictor of weight regain.

Dietary protein and amino acids suppress food intake through redundant peripheral and central mechanisms, including vagal signaling via gut peptides (CCK, GLP-1, PYY) and central metabolic sensing (mTOR/AMPK) in the hypothalamus.

To leverage protein for appetite control, focus on its physiological effects rather than taste. Protein triggers gut hormones (CCK, GLP-1, PYY) and central brain sensors (mTOR/AMPK) that signal fullness. This is a robust biological mechanism, not just a matter of liking the food. Ensure your protein sources are well-balanced in essential amino acids to maximize this effect.

Leucine is a specific amino acid that modulates food intake centrally by activating mTOR and suppressing AMPK in the hypothalamus, mimicking the effects of high-protein diets.

Ensure your protein intake includes sufficient leucine, as it directly activates brain sensors (mTOR) that reduce hunger. This is a key driver of protein's satiating power, independent of total calories.

Fasting for 18 hours or more significantly reduces circulating PCSK9 levels in humans, independent of changes in LDL cholesterol.

Fasting for 18 hours or more significantly lowers circulating PCSK9, a protein that regulates LDL receptors. However, this does not necessarily translate to lower LDL cholesterol levels in the blood, as other regulatory mechanisms (like LDL receptor expression) may compensate. This suggests that PCSK9 levels alone are not a perfect predictor of LDL outcomes in fasting states.

Insulin resistance (IR) and hyperinsulinemia are key etiological components of PCOS that drive excessive ovarian androgen production, leading to reproductive dysfunction, independent of but amplified by obesity.

Understanding that insulin resistance drives PCOS symptoms is crucial. Treating insulin resistance through diet and lifestyle can help reduce androgen levels and restore ovulation, even without significant weight loss.

Higher dietary fiber intake is associated with a 25% reduction in all-cause mortality in adults with established cardiovascular disease.

If you have heart disease, eating more fiber-rich foods like whole grains, fruits, and vegetables can help you live longer. Studies show that people with heart disease who eat more fiber have a 25% lower risk of dying from any cause compared to those who eat less fiber.

Evening chronotypes exhibit a significantly delayed subjective sleepiness rhythm (5–9 hours phase shift) compared to morning chronotypes, whereas endogenous circadian markers (core temperature and melatonin) show only a modest 2–3 hour delay, suggesting that subjective alertness drives sleep timing rather than biological phase alone.

If you are an evening type, your biological clock (melatonin/temperature) is only slightly delayed compared to morning people, but your feeling of sleepiness is delayed much more (5-9 hours). This mismatch causes you to stay up late not because your body demands it biologically, but because you don't feel sleepy. To fix this, you must align your bedtime with your biological ability to sleep (temperature/melatonin onset) rather than waiting until you feel subjectively sleepy, which happens too late for healthy sleep duration.

Increased per capita fast food consumption is independently associated with higher mean population body mass index (BMI) in high-income countries, with each 1-unit increase in annual fast food transactions linked to a 0.033 kg/m² increase in BMI.

In high-income countries, higher availability and consumption of fast food are linked to higher average body weights. This link is partly driven by the soft drinks often consumed with fast food, rather than just the fat or total calories in the food itself. Policy changes that restrict market deregulation may help curb the spread of fast food and its associated health impacts.

During submaximal exercise, low muscle glycogen levels increase fat oxidation primarily through heightened AMPK activation, whereas high glycogen levels limit fat oxidation by sequestering free carnitine into acetylcarnitine, despite similar malonyl-CoA reduction in both conditions.

To maximize fat oxidation during exercise, be aware that high muscle glycogen can limit fat burning by consuming free carnitine. While low glycogen boosts fat oxidation via AMPK, high glycogen creates a bottleneck where carnitine is used to buffer acetyl-CoA instead of transporting fat into mitochondria. Moderate intensity exercise with moderate glycogen may offer a balance, but very high intensity with high glycogen may shift fuel use toward carbohydrates due to this carnitine limitation.

Higher total daily sedentary time is independently associated with increased cancer mortality risk in middle-aged and older adults, regardless of moderate-to-vigorous physical activity (MVPA) levels.

If you are over 45, your total daily sitting time matters for your long-term survival risk, independent of how much you exercise. Use an accelerometer or pedometer to track total sedentary minutes. Aim to reduce total sitting time, not just to 'get your workout in,' but to lower your baseline risk profile.

HMB supplementation at a moderate dose (38 mg/kg/day, approx 3g/day) increases fat-free mass gains during 8 weeks of resistance training in untrained men, whereas a higher dose (76 mg/kg/day, approx 6g/day) provides no additional FFM benefit.

If you are new to resistance training, taking 3 grams of HMB daily (split into 3 doses) alongside your workouts may help you gain more muscle mass than training alone. However, taking 6 grams daily offers no extra muscle benefit compared to 3 grams. You do not need to take high doses to see the FFM benefit.

HMB supplementation at a high dose (76 mg/kg/day) increases peak isokinetic torque at specific velocities, but does not increase 1-repetition maximum (1RM) strength compared to placebo.

Taking 6g of HMB daily might improve your muscle's ability to produce force at certain speeds during exercise, but it will not necessarily help you lift a heavier weight for one repetition. Focus on the moderate dose (3g) if your goal is muscle mass.

HMB supplementation (38 or 76 mg/kg/day) reduces plasma creatine phosphokinase (CPK) levels 48 hours after the initial resistance training bout compared to placebo, indicating reduced muscle damage.

Taking HMB (3g or 6g daily) may help reduce muscle damage markers (CPK) right after your first intense workouts, potentially aiding early recovery. However, this reduction in damage markers did not translate to greater strength or muscle mass gains in this study.

Among adults aged 50–95, abdominal adiposity (measured by waist circumference) is a significantly stronger predictor of insulin resistance than cardiovascular fitness (VO2max) or whole-body adiposity (BMI/fat percentage).

If you are over 50, your waist size matters more for your blood sugar health than your cardio fitness level. While staying active is beneficial, focusing on reducing abdominal fat (measured by waist circumference) is the most effective way to lower insulin resistance risk. Do not assume high fitness cancels out the risks of a large waistline.

High work-related stress and increased workload cause a flattened diurnal cortisol pattern (specifically elevated evening levels) and reduced total sleep time, impairing physiological recovery.

If you are experiencing high work stress, expect your sleep to suffer and your stress hormones (cortisol) to remain elevated into the evening. This prevents proper physiological recovery. To mitigate this, you must actively create a buffer between work and sleep (e.g., no work after a specific time) to allow cortisol to drop and sleep duration to recover, as the body does not automatically 'switch off' under high workload.

Visceral fat mass exhibits the strongest positive correlation with insulin resistance (measured by HOMA-IR) among all adipose tissue depots and obesity indices.

If you are concerned about insulin resistance, looking at your weight (BMI) alone is not enough. Visceral fat (belly fat) is the strongest predictor of metabolic risk. Even if your BMI is normal, high visceral fat can lead to insulin resistance. Prioritize measuring waist circumference or assessing body composition over BMI alone for metabolic health assessment.

Regular aerobic exercise increases HDL cholesterol levels and enhances Reverse Cholesterol Transport (RCT) efficiency by upregulating key receptors (ABCA1, ABCG1, SR-B1) and enzymes (LCAT, CETP).

Engage in regular aerobic exercise, such as walking or cycling. You do not need extreme intensity; even moderate activities like walking 10,000 steps three times a week can improve your HDL cholesterol and overall lipid profile. Consistency is key, and combining aerobic with resistance training may offer additional benefits.

Dietary strategies that replace carbohydrates with saturated fats (e.g., cheese, meat, butter) or include monounsaturated/polyunsaturated fats (e.g., olive oil) can increase HDL cholesterol levels.

Consider reducing your carbohydrate intake and replacing it with healthy fats, such as those found in olive oil, nuts, or even moderate amounts of saturated fats from cheese and meat. This dietary shift can help increase your HDL cholesterol levels.

Higher dairy product consumption is associated with a modest reduction in BMI and lower risk of obesity, particularly in overweight or obese individuals, whereas cheese consumption may be positively associated with obesity prevalence.

To support weight management, prioritize milk and yogurt over cheese. The evidence suggests these lower-fat dairy options are associated with lower BMI and reduced obesity risk, especially if you are already overweight. Aim for higher calcium intake from these sources (around 800-1200 mg/d) as part of a balanced diet, but recognize the effect is modest and not a substitute for overall energy balance.

Brown adipose tissue (BAT) plays a critical role in glucose disposal and triglyceride clearance, acting as a sink for circulating lipids and glucose, which may protect against insulin resistance and obesity.

Your brown fat doesn't just burn heat; it also helps clear fats and sugar from your blood. This metabolic function might be one reason why maintaining or activating brown fat is linked to better metabolic health and lower risk of obesity-related issues.

Caffeine improves endurance performance only in individuals with the CYP1A2 AA genotype (fast metabolizers), while impairing performance in those with the CC genotype.

If you use caffeine for performance, know your CYP1A2 genotype. If you are a 'fast metabolizer' (AA), standard doses (2-4 mg/kg) likely boost your endurance. If you are a 'slow metabolizer' (CC), caffeine may actually hurt your performance and increase health risks like hypertension. If you are intermediate (AC), you likely see no benefit. Genetic testing can prevent wasted effort or performance loss.

The metabolic response (specifically butyrate vs. propionate production) to dietary fiber supplementation is determined by the donor's baseline microbiota composition (Bacteroidaceae-Ruminococcaceae vs. Prevotellaceae-Ruminococcaceae dominance) rather than the specific type of fiber consumed.

Prebiotic fibers do not work in a vacuum; your existing gut bacteria dictate the health benefits you get. If your microbiome is dominated by Bacteroidaceae, fibers like inulin or beta-glucan will likely boost butyrate. If dominated by Prevotellaceae, they will likely boost propionate. There is no single 'best' fiber for everyone; the effect is personalized by your baseline microbiome.

Caloric restriction (20-40% reduction) extends healthspan and lifespan in model organisms and improves cardiometabolic markers in humans, but is associated with reduced bone mineral density.

Strict caloric restriction (20-40% reduction) is the most proven method for extending healthspan in animals and shows promise in humans, but it comes with side effects like bone loss. If you attempt this, you must combine it with exercise to protect your bones. However, because it is difficult to maintain, consider less invasive alternatives like intermittent fasting or specific macronutrient restrictions which may offer similar benefits with fewer side effects.