Browse the evidence

Higher levels of social and political globalization are significantly associated with an increased risk of overweight and obesity in women aged 15-49 in low- and middle-income countries, primarily through mechanisms of nutritional transition and reduced energy expenditure.

For policymakers in LMICs, focusing solely on trade liberalization (economic globalization) may not be enough to curb obesity. Strategies must address the social and political dimensions of globalization, such as urban planning, media influence, and food marketing, which drive the 'nutritional transition' towards higher calorie intake and lower physical activity.

Cold exposure induces adaptive thermogenesis primarily through non-shivering thermogenesis (NST) mediated by brown adipose tissue (BAT) and UCP1, regulated by the hypothalamus.

Exposure to cold temperatures can activate brown fat, which burns calories to generate heat. This process, called non-shivering thermogenesis, is regulated by your hypothalamus. While not a replacement for diet and exercise, leveraging cold exposure (like cooler room temps) may support metabolic health.

PPARα activation suppresses the liver secretome (including complement and coagulation factors) to conserve energy during fasting, whereas FXR activation induces secretion to support nutrient processing in the fed state.

Your liver actively manages energy by adjusting how much protein it secretes based on whether you are eating or fasting. In the fed state, it produces more proteins (like clotting factors and complement) to support nutrient processing. In the fasted state, it reduces this production to save energy. This suggests that nutritional strategies, particularly for those with metabolic issues or undernutrition, should consider the timing of nutrient intake to align with these natural hormonal switches (PPARα for fasting, FXR for feeding).

Calorie restriction extends lifespan and improves metabolic health in mammals by upregulating SIRT1 and SIRT3, which deacetylate and activate metabolic enzymes and transcription factors to shift cells from glycolysis to oxidative phosphorylation.

Calorie restriction (reducing intake to 60-70% of ad libitum levels) activates sirtuins (SIRT1 and SIRT3), which shift metabolism from glycolysis to oxidative phosphorylation, improving insulin sensitivity and extending lifespan in mice. While direct application to humans requires more research, the mechanism suggests that metabolic flexibility and mitochondrial health are key to longevity.

Estrogen regulates mitochondrial function, including biogenesis and respiratory chain activity, and loss of estrogen leads to mitochondrial dysfunction which contributes to insulin resistance.

Estrogen helps your cells produce energy efficiently. After menopause, the drop in estrogen can impair your mitochondria, leading to fatigue and weight gain. This is one reason why metabolic rate slows down after menopause.

Elevated plasma acylcarnitine levels, particularly long-chain species, are biomarkers of insulin resistance and incomplete fatty acid oxidation in Type 2 Diabetes, reflecting mitochondrial stress rather than directly causing insulin resistance.

High levels of acylcarnitines in the blood are a sign of how your body is processing fats and sugars, indicating mitochondrial stress in T2D. This helps doctors understand the severity of metabolic dysfunction.

In young military recruits undergoing high-intensity training, daily food intake does not acutely regulate or compensate for daily energy expenditure, as there is no significant day-to-day correlation between the two.

Do not rely on your daily hunger to tell you how much to eat based on your daily activity. In high-activity environments like military training, people do not automatically eat more on heavy training days. To maintain energy balance, you must consciously manage your food intake regardless of day-to-day exercise variations.

Dietary restriction (DR) extends lifespan by triggering mitochondrial adaptations, including increased sirtuin activity and mitochondrial biogenesis via PGC-1α.

Consider dietary restriction as a primary strategy for longevity. It works by activating sirtuins and boosting mitochondrial biogenesis (via PGC-1α). While the exact dose isn't defined here, the mechanism suggests that reducing caloric intake triggers protective mitochondrial adaptations.

Obesity is associated with a specific gut microbiota composition characterized by a higher Firmicutes-to-Bacteroidetes ratio, lower bacterial gene richness, and increased gut permeability leading to metabolic endotoxemia.

Obesity is linked to a less diverse gut microbiome with specific bacterial imbalances. While you cannot directly 'buy' a healthy microbiome, eating a diverse, fiber-rich diet supports the bacteria that help regulate energy and inflammation.

Bariatric surgery effectively treats obesity by reducing stomach volume and nutrient absorption, and inducing faster satiety.

For severely obese individuals, bariatric surgery is a viable option that mechanically restricts food intake and alters satiety signals. It is typically reserved for cases where lifestyle changes have not been sufficient.

Cideb deficiency reduces hepatic lipogenesis by downregulating SREBP1c and its downstream targets (ACC, FAS, SCD1), while simultaneously increasing fatty acid oxidation.

This study identifies Cideb as a key regulator of liver fat balance. By reducing Cideb activity, the liver shifts from storing fat (lipogenesis) to burning it (oxidation). This suggests that therapies targeting Cideb or its regulators (like SREBP1c) could be effective in treating fatty liver disease and obesity by rebalancing these metabolic pathways.

SIRT1 activation in the hypothalamus regulates energy metabolism and circadian rhythms, influencing susceptibility to diet-induced obesity and metabolic disorders.

Diet and exercise influence brain SIRT1 levels, which in turn regulate hunger and energy expenditure. This suggests that lifestyle interventions work partly by modulating central brain mechanisms, not just peripheral calorie burning.

Resting metabolic rate (RMR) is highly homogeneous in healthy young adults after adjusting for metabolically active tissue (total body potassium), with protein turnover explaining only a small but significant fraction (approx. 20%) of the remaining variability.

If you are healthy, your resting metabolism is likely very similar to others of your size and active tissue mass. Don't blame 'slow metabolism' for weight issues; focus on body composition. Protein turnover plays a minor role in RMR differences.

Increased body fat is associated with elevated resting metabolic rate and protein turnover, even after accounting for lean body mass (total body potassium).

Having more body fat does not mean your metabolism is 'slow' relative to your lean mass. In fact, higher fat mass is associated with higher metabolic rate and protein turnover, even when you account for your lean tissue.

Inhibition of MuRF1 and MuRF2 prevents age-related body fat accumulation in mice, resulting in a lean phenotype despite increased muscle mass.

In mice, blocking MuRF1/2 prevents fat gain during aging. This is likely due to the high energy cost of maintaining larger muscles and potentially direct effects on fat metabolism. This is not a current human intervention, but it suggests that increasing muscle metabolic activity might help manage body fat.

Sedentary behavior interventions do not produce significant changes in fat-free mass, diastolic blood pressure, fasting glucose, HbA1c, LDL cholesterol, or triglycerides.

Do not expect sedentary reduction to significantly change your blood sugar levels (HbA1c, fasting glucose), cholesterol (LDL, Triglycerides), or muscle mass. While these metrics may show slight beneficial trends, the changes are not statistically significant. Focus on the proven benefits like improved blood pressure and insulin sensitivity instead.

Caloric restriction (CR) without malnutrition extends healthspan and lifespan across multiple species by modulating nutrient-sensing pathways such as mTORC1, AMPK, and Sirtuins.

To potentially extend healthspan, reduce your caloric intake by 20-30% below your maintenance level without sacrificing essential nutrients. Focus on nutrient-dense foods to avoid malnutrition while triggering metabolic adaptations like autophagy and improved insulin sensitivity.

Excess dietary protein cannot be stored in the body and is instead oxidized for energy or converted to glucose/urea, meaning high protein intake does not directly lead to increased tissue storage without concurrent resistance training.

Do not expect high protein intake alone to build muscle or add mass. If you are not exercising, your body will burn the excess protein for energy or excrete it as urea. To utilize protein for tissue growth, you must combine adequate intake with resistance training.

During short-term caloric restriction (800 kcal/day), switching from a standard mixed diet to a ketogenic diet increases the rate of total weight loss solely through increased water excretion, with no significant difference in the rate of fat loss between the two diets.

If you are trying to lose fat, the speed at which you lose fat is determined by your calorie deficit, not whether you eat carbs or not. A ketogenic diet might make the scale drop faster initially due to water loss, but you are not burning fat faster than if you ate a standard low-calorie diet. Focus on maintaining your calorie deficit consistently.

Deficiency in the histone demethylase JHDM2a causes adult-onset obesity, metabolic syndrome, and insulin resistance in mice through reduced energy expenditure and impaired fat oxidation.

This research highlights that obesity is not just about calories in vs. calories out, but also involves complex epigenetic regulation of how your body burns fat. In mice, a specific enzyme (JHDM2a) controls genes that determine energy expenditure. When this enzyme is missing, the body burns less fat and stores more, leading to obesity regardless of food intake. This suggests that metabolic health is deeply tied to gene expression regulation, not just behavior.

Human obesity is primarily driven by the interaction of ancestral energy-conserving genetic adaptations (thrifty genotype) with a modern environment of energy abundance and physical inactivity.

Understand that your body is biologically wired to store fat efficiently because of your evolutionary history. In a modern world with abundant food and low activity, this wiring promotes weight gain. This is not a moral failing but a biological reality. Management requires acknowledging this mismatch and structuring your environment (food access, activity levels) to counteract these ancestral drives.

Captive primates and wild primates with access to abundant, low-effort food sources (like garbage) develop obesity and metabolic abnormalities, demonstrating that energy storage capacity exists in primates when foraging costs are removed.

Your body's ability to store fat is a survival mechanism. When you reduce physical activity (like sitting at a desk) and have easy access to food, your body will store that energy as fat, just as it does in captive primates. To manage weight, you must either increase energy expenditure or restrict energy intake to match your lower activity level.

Persons with chronic spinal cord injury, particularly those with tetraplegia and complete lesions, have significantly lower physical activity levels than able-bodied individuals, contributing to obesity.

Standard daily tasks like pressure relief and bowel programs are sedentary and do not burn significant calories. To prevent obesity, you must engage in structured physical activity (exercise) to increase your total daily energy expenditure.

Resting metabolic rate (RMR) in SCI patients is lower than in able-bodied individuals, but this difference is largely explained by reduced fat-free mass and altered sympathetic nervous system activity, not by an inherent inefficiency of fat-free tissue.

Your lower resting metabolic rate is due to having less muscle mass and altered nerve signaling, not because your cells are inefficient. Focus on maintaining muscle mass and accurate calorie intake rather than assuming your metabolism is 'broken'.