Browse the evidence

Leptin levels are higher in women for any given fat mass and are critical for female fertility, with low leptin reducing fertility in women but not men.

For women, maintaining a minimum level of body fat is crucial for fertility because leptin signals reproductive readiness. Extremely low body fat can lead to infertility, a biological safeguard not present in men.

Circulating Adipocyte Fatty Acid–Binding Protein (A-FABP) levels are significantly elevated in overweight and obese individuals and correlate positively with components of metabolic syndrome, including insulin resistance, dyslipidemia, and hypertension.

This research highlights that Adipocyte Fatty Acid–Binding Protein (A-FABP) is a circulating marker that rises with obesity and correlates with metabolic risks like insulin resistance and high blood pressure. While measuring A-FABP is not a standard clinical test for weight loss, the findings reinforce that excess adipose tissue actively contributes to metabolic dysfunction through secreted proteins. Managing body weight and reducing visceral fat are the primary levers to lower these biomarkers and improve metabolic health.

Obesity and post-diagnosis weight gain in breast cancer patients are associated with significantly increased risks of disease recurrence and mortality.

For breast cancer patients, maintaining a healthy weight or losing weight if overweight is critical for reducing the risk of recurrence and death. This is not just about aesthetics; it is a clinical priority supported by strong observational data and hormonal mechanisms. Patients should engage in weight loss programs combining diet, physical activity, and behavioral therapy.

Post-activation potentiation (PAP) is a distinct physiological phenomenon from post-activation performance enhancement (PAPE), characterized by a short half-life (~28s) driven by myosin light chain phosphorylation, whereas PAPE occurs 6-10 minutes post-activity and is likely driven by increased muscle temperature and activation rather than PAP mechanisms.

Do not assume that a heavy warm-up improves your subsequent performance solely through 'post-activation potentiation.' The paper suggests that PAP (a biochemical state) fades quickly (~30s), while voluntary performance gains (PAPE) peak later (6-10 minutes) and are likely driven by increased muscle temperature and neural activation. Design your warm-up to allow time for these physiological changes to occur, and recognize that 'potentiation' is not the sole or primary driver of late-phase performance boosts.

Peripheral administration of PYY3-36 reduces food intake, and bariatric surgery works in part by causing an exaggerated postprandial PYY3-36 surge.

If you undergo bariatric surgery, part of why it works is that your body releases more PYY3-36, a hormone that makes you feel full. This hormonal change helps maintain weight loss long-term, complementing the physical restriction of the surgery.

Restricting sleep to 5 hours per night for one week significantly reduces insulin sensitivity in healthy men, as measured by both intravenous glucose tolerance tests and euglycemic-hyperinsulinemic clamps.

If you are a healthy adult, restricting your sleep to 5 hours a night for just one week can significantly reduce your body's ability to handle glucose (insulin sensitivity). This happens even if you feel alert (especially if taking stimulants like modafinil). To maintain metabolic health, prioritize getting adequate sleep (7+ hours) rather than sacrificing it for extra waking hours.

Hip circumference is an independent predictor of metabolic risk; a smaller hip circumference (for a given waist circumference) is associated with increased risk of cardiovascular disease and type 2 diabetes.

Measure your hip circumference. If it is small relative to your waist, your risk for metabolic disease is higher. Building leg muscle and maintaining peripheral fat may offer some metabolic protection.

Dietary protein restriction, independent of energy intake, robustly increases circulating FGF21 levels in both rodents and humans, whereas energy restriction alone decreases or does not increase FGF21.

If you are consuming very low amounts of protein (e.g., <10% of calories), your body produces significantly more FGF21, a hormone that alters metabolism and growth. This response is driven by the lack of protein, not by how many calories you eat. Ensuring adequate protein intake prevents this specific hormonal stress response.

Adipose tissue insulin sensitivity is inversely correlated with adipose cell size; larger cells exhibit diminished insulin responsiveness, which is reversible through weight loss and cell size reduction.

If you are obese, your fat cells may be less sensitive to insulin, requiring higher insulin levels to manage blood sugar. This is not a permanent defect; losing weight and reducing fat cell size can restore normal insulin sensitivity, effectively reversing this specific metabolic hurdle.

Orlistat is the only currently available anti-obesity drug for long-term management due to its favorable cardiovascular safety profile compared to withdrawn agents like sibutramine and rimonabant.

Orlistat is the only long-term anti-obesity drug currently available because it does not carry the cardiovascular risks of older drugs. It works by blocking fat absorption. You must take 120mg with meals. Expect gastrointestinal side effects if you eat fat; managing your fat intake can reduce these side effects. It provides modest weight loss (~3kg over a year) but improves metabolic markers.

Obesity, insulin resistance, inflammation, and oxidative stress are common metabolic pathways linking diabetes and hypertension, with central obesity acting as a primary cause of the metabolic syndrome.

Managing weight and reducing visceral fat is the most effective way to address the root causes of both diabetes and high blood pressure. Focus on lifestyle optimization (diet, exercise) to reduce insulin resistance and inflammation, as these are the shared drivers of both conditions.

Long-term endurance exercise prevents age-related declines in insulin sensitivity and mitochondrial oxidative capacity, rendering these functions comparable to those of young sedentary individuals.

If you are an older adult concerned about metabolic health, habitual endurance exercise (cycling or running, ~1 hour, 6 days/week) can normalize your insulin sensitivity and mitochondrial function to levels seen in young sedentary people. Focus on consistency rather than intensity; the key is long-term adherence, not short-term bursts.

Long-term endurance exercise elevates SIRT3 expression to levels comparable to young individuals, potentially linking exercise benefits to caloric restriction pathways.

Endurance exercise may trigger longevity pathways (SIRT3) similar to caloric restriction. You do not need to starve yourself to gain these molecular benefits; consistent aerobic activity achieves the same SIRT3 elevation.

Cortisol circadian rhythm contributes to decreased insulin sensitivity in the evening, as elevated morning cortisol is associated with high insulin sensitivity, while lower evening cortisol coincides with reduced sensitivity.

Your natural cortisol rhythm affects how sensitive your cells are to insulin. Morning cortisol helps keep you sensitive, while the natural drop in the evening contributes to reduced sensitivity. This is a normal physiological pattern, not necessarily a sign of 'stress' in the negative sense.

GLP-1 receptor agonists lower blood glucose and HbA1c in type 2 diabetes by stimulating glucose-dependent insulin secretion, inhibiting glucagon secretion, slowing gastric emptying, and reducing food intake, with effects preserved in diabetic subjects unlike GIP.

GLP-1 receptor agonists (like exenatide/exendin-4 and liraglutide/NN2211) are effective injectable treatments for type 2 diabetes. They work by mimicking a gut hormone to boost insulin when blood sugar is high, slow down digestion, and reduce appetite. Unlike older gut hormones (GIP), GLP-1 works well even in people with established diabetes. While they require injections and can cause nausea, they significantly lower blood glucose and HbA1c.

DPP-IV inhibitors lower blood glucose in type 2 diabetes by preventing the degradation of endogenous incretins (GLP-1 and GIP), offering an oral alternative to injectable GLP-1R agonists.

DPP-IV inhibitors are oral medications that work by stopping the body from breaking down its own natural glucose-lowering hormones (incretins). They are effective in lowering blood glucose and HbA1c in people with type 2 diabetes. They offer an oral alternative to injectable GLP-1R agonists, though they may be less potent.

One week of insufficient sleep (approx. 5.7 hours per 24 hours) disrupts the human blood transcriptome by reducing the number of genes with circadian expression profiles and decreasing their circadian amplitude.

Consistently getting less than 7-8 hours of sleep for even one week changes how your genes express themselves, specifically dampening the natural daily rhythms of immune and metabolic genes. This makes your body more vulnerable to stress and inflammation. Prioritize consistent sleep duration, not just occasional recovery.

Prior insufficient sleep significantly increases the number of genes that respond to subsequent acute total sleep deprivation, indicating an intensified stress response.

If you are already sleep-deprived, staying awake for an extra day (acute sleep loss) triggers a much larger inflammatory and stress response in your blood than if you were well-rested. This suggests that chronic sleep debt makes you biologically more sensitive to acute stressors.

Insufficient sleep alters the phase and waveform of circadian gene expression, narrowing the window of peak expression for night-active genes and shifting the timing of immune and metabolic gene clusters.

Sleep restriction doesn't just reduce the amount of 'good' gene expression; it changes WHEN those genes are active. This misalignment can disrupt the timing of immune responses and metabolism, potentially contributing to health issues even if total sleep time is recovered later.

Estrogen deficiency during menopause causes a shift in fat distribution from subcutaneous to visceral (abdominal) adipose tissue and promotes metabolic dysfunction, which can be mitigated by estrogen replacement therapy.

If you are a postmenopausal woman experiencing rapid abdominal weight gain, this is likely driven by the loss of estrogen, not just your diet. While lifestyle changes are always important, the paper suggests that Hormone Replacement Therapy (HRT), particularly transdermal estrogen, may help reverse this specific visceral fat accumulation and improve metabolic health in women under 60, provided the benefits outweigh individual risks like breast cancer.

Administering low-dose leptin to restore circulating levels to pre-weight-loss values reverses the metabolic, autonomic, and neuroendocrine adaptations (increased muscle efficiency, decreased energy expenditure, and reduced sympathetic tone) that promote weight regain in humans.

If you have lost weight, your body fights back by becoming more efficient and slowing your metabolism. This study suggests that replacing the leptin hormone lost with fat tissue (to levels you had before losing weight) can reverse these 'starvation mode' adaptations, potentially helping you maintain your weight loss without needing to eat less or exercise more than your body naturally demands.

Psychosocial stress, particularly the anticipation of high demands or effort, causes impaired sleep characterized by shortened duration, fragmentation, and reduced slow-wave sleep (SWS).

If you are stressed, your sleep will likely suffer, especially if you are anticipating difficult tasks. This is driven by physiological arousal (cortisol, heart rate) and cognitive worry. To mitigate this, try to reduce the cognitive load of anticipating work demands before bed, as this anticipation is a primary driver of sleep fragmentation and reduced deep sleep.

Impaired sleep acts as a stressor itself, increasing levels of traditional stress markers like cortisol and exacerbating the effects of initial stress.

Poor sleep doesn't just make you tired; it puts your body in a physiological state similar to being stressed (high cortisol, inflammation). Prioritizing sleep is therefore a direct way to lower your overall stress burden.

Untreated thyroid dysfunction (both hyper- and hypothyroidism) impairs metabolic control in diabetic patients, exacerbating glycemic instability and increasing the risk of microvascular complications.

If you have diabetes, your thyroid health directly impacts your blood sugar control. Untreated thyroid issues (even subclinical ones) can make your diabetes harder to manage. You should be screened for thyroid dysfunction (TSH, TPO antibodies) regularly, and if found, treating the thyroid issue is essential to achieving stable glucose levels.