Browse the evidence

Using a ±1 standard deviation (SD) cut-off to screen out inaccurate dietary energy intake reports (comparing reported intake to predicted total energy expenditure) is preferable to using a ±2 SD cut-off or no cut-offs when analyzing relationships between diet and health outcomes like BMI.

If you are analyzing dietary data to understand health outcomes, do not just throw out the most extreme outliers. Use a stricter screening method (like comparing reported intake to predicted energy needs using a ±1 SD threshold) to remove inaccurate reporters. This reveals the true relationship between diet and body weight, which is often hidden if you rely on self-reported 'usual' intake or loose exclusion criteria.

A complete shift to plant-based protein (vegetarian diet) reduces total agricultural land use and GHG emissions compared to the HHEP diet, despite requiring more arable land for crops.

Shifting to plant-based protein sources (legumes, seeds, nuts) reduces GHG emissions and pasture land use compared to animal-based proteins. While it may require more arable land for crops, the overall environmental footprint is lower.

Total energy expenditure (TEE) and physical activity level (PAL) decline progressively throughout adult life (from age 20 to 96) in both normal weight and overweight individuals, primarily driven by a decrease in physical activity rather than just basal metabolic rate changes.

As you age, your body burns fewer calories, but this isn't just because your organs slow down. A large part of the drop comes from moving less (lower Physical Activity Level). To maintain your weight, you need to account for this gradual decline in energy expenditure (about 150 kcal/day less per decade for normal-weight adults) by adjusting your food intake or increasing your physical activity levels.

Genetic factors account for specific portions of BMI variability through three measurable metabolic traits: metabolic rate (12%), respiratory quotient/fat oxidation (5%), and spontaneous physical activity (10%), leaving 40% attributable to food intake regulation.

Your body burns calories differently based on genetics. Some people burn less at rest (metabolic rate), oxidize less fat (high RQ), or move less unconsciously (low NEAT). Understanding this helps explain why some people gain weight easily despite similar calorie intake to others.

In free-living humans, increased physical activity triggers energy compensation, where basal metabolic rate (BEE) decreases such that only ~72% of the calories burned through activity translate into increased total energy expenditure (TEE).

When you exercise, your body naturally lowers your resting metabolism to save energy. On average, you only get 72% of the 'extra' calories burned from exercise added to your total daily burn. This doesn't mean exercise is bad, but it means you cannot simply 'eat back' all the calories you burned. Weight loss requires managing intake, as exercise alone faces a biological ceiling due to this compensation.

The degree of energy compensation increases with body fat mass (FM), with individuals at the 90th percentile of BMI compensating ~49% of activity calories compared to ~28% for those at the 10th percentile.

If you have higher body fat, your body will likely compensate more strongly for exercise by lowering your resting metabolism. This means exercise alone will be less effective for weight loss in higher-fat individuals. To lose weight, you likely need to combine exercise with dietary changes to create a deficit that overcomes this higher compensation rate.

Unilateral aerobic exercise (e.g., single-leg cycling) can elicit greater skeletal muscle metabolic adaptations than bilateral exercise when performed at the same relative intensity, due to the elimination of central limitations (bilateral deficit) that restrict workload in bilateral training.

If you are doing high-intensity aerobic training and want to maximize metabolic adaptations in your muscles, consider single-leg cycling or similar unilateral aerobic exercises. Because your heart and lungs limit how hard you can push when using both legs, using one leg at a time allows you to work that muscle harder, potentially leading to greater metabolic improvements.

Roux-en-Y gastric bypass (RYGB) surgery produces the greatest long-term weight loss and is the most cost-effective intervention for severe obesity (BMI ≥ 35 kg/m2) compared to lifestyle interventions or pharmacotherapy.

For individuals with a BMI of 35 or higher, Roux-en-Y gastric bypass surgery is the most effective and cost-effective treatment for long-term weight loss, significantly outperforming lifestyle interventions and medication like orlistat. While it involves surgery and higher upfront costs, it leads to greater sustained weight reduction.

Circadian misalignment and sleep loss disrupt peripheral clocks in skeletal muscle, leading to impaired mitochondrial function, reduced glucose tolerance, and increased insulin resistance.

Prioritize sleep for metabolic health. Poor sleep disrupts your body's internal clock, leading to worse blood sugar control and reduced mitochondrial efficiency. This happens even if you are eating well and exercising. Aim for 7-9 hours of quality sleep to support your metabolic function.

Reducing daily step counts from ~10,500 to ~1,344 for two weeks causes a 17% decline in skeletal muscle insulin sensitivity, a 7% decrease in cardiovascular fitness, and a 3% reduction in lean leg mass.

Do not assume that staying home for a short period is metabolically neutral. If you cannot maintain your usual activity levels, you must actively manage your energy intake and incorporate movement (even small bouts) to prevent rapid declines in insulin sensitivity and muscle mass.

Skeletal muscle hypertrophy can occur in an energy deficit, particularly in resistance training-naive, overweight, or obese individuals, challenging the textbook requirement for an energy surplus.

If you are new to resistance training or have higher body fat, you do not need to eat in a caloric surplus to build muscle. You can build muscle while losing fat by focusing on high protein intake and consistent resistance training. If you are already highly trained and lean, a small surplus may be more beneficial, but it is not strictly required for all populations.

Substantial weight loss (via bariatric surgery or intensive lifestyle) reduces systemic inflammation and cardiovascular risk, whereas modest weight loss may not translate to CVD benefits.

To protect your heart, you need to lose at least 10% of your body weight. Modest weight loss (5-10%) improves blood sugar and cholesterol but may not prevent heart attacks. Bariatric surgery is the most effective way to achieve this and reduce inflammation, but intensive lifestyle changes can also work if sustained.

Pregnant women with obesity should not increase energy intake during the second and third trimesters; maintaining early-pregnancy energy intake levels achieves recommended gestational weight gain by mobilizing maternal fat mass.

If you have obesity and are pregnant, do not try to increase your daily calories in the second and third trimesters. Instead, aim to eat roughly the same amount you ate in early pregnancy. Your body will use your stored fat to support the baby's growth, which helps you stay within healthy weight gain limits without risking excess fat accumulation.

Non-exercise activity thermogenesis (NEAT) is the most variable component of total daily energy expenditure, ranging from 15% to over 50% of TDEE, and serves as a primary regulator of body weight and obesity risk.

To manage weight, prioritize increasing your daily non-exercise movement (NEAT) such as walking, standing, and fidgeting, rather than relying solely on structured exercise. NEAT is the most variable part of your energy expenditure and can range from 15% to over 50% of your total daily energy needs. Small changes in daily activity levels have a substantial cumulative impact on energy balance.

NEAT is regulated by biological factors (weight, gender, body composition) and environmental factors (occupation, urbanization), and changes in NEAT subtly accompany experimentally-induced changes in energy balance.

Understand that your daily movement (NEAT) is influenced by your job, environment, and genetics. While you cannot change your genetics, you can modify your environment to encourage more movement (e.g., walking to work, standing desks). NEAT changes subtly in response to energy balance, so increasing daily movement can help counteract weight gain.

Sustained caloric restriction (approx. 12-25% reduction) in healthy non-obese adults for two years is safe and well-tolerated, with no deaths and only minor adverse events, despite causing modest bone mineral density loss and hematocrit drops.

If you are healthy and not obese, restricting calories by about 12-25% for two years is generally safe and well-tolerated. You should take calcium and multivitamins, and get regular check-ups to monitor bone density and blood counts, as these may drop slightly.

SGLT2 inhibitors produce modest weight loss (2-5 kg) in Type 2 Diabetes, which is significantly less than the ~10 kg/year predicted by caloric loss from glycosuria due to compensatory metabolic adaptations.

If you are taking an SGLT2 inhibitor for diabetes, expect a modest weight loss of 2-5 kg, not the dramatic loss you might calculate from urine sugar loss. This modest loss is still beneficial for your heart and kidneys. Use this weight change as a motivational anchor to support other healthy lifestyle changes, rather than relying on the drug alone for significant fat loss.

Higher habitual physical activity (measured as Physical Activity Level, PAL) is associated with significantly higher fat-free mass (FFM) during growth (under 18 years) and in early adulthood, but this positive association diminishes and is counteracted by aging in older adults.

Stay physically active throughout your life to maximize your muscle mass. The biggest benefits for building fat-free mass occur during growth and early adulthood (up to age 30). In older age, exercise won't fully stop muscle loss, but active individuals still retain significantly more muscle than sedentary peers, which helps maintain independence and functional capacity.

Weight loss interventions, including bariatric surgery and dietary changes, reduce the risk of ventricular arrhythmias and sudden cardiac death in obese patients by correcting electrophysiological abnormalities.

Losing weight through diet or surgery is a powerful way to protect your heart from dangerous rhythms. It doesn't just change your appearance; it physically corrects the electrical signals in your heart (shortening the QT interval) and reduces the metabolic stress that triggers arrhythmias. Discuss weight management strategies with your cardiologist.

Glucagon receptor activation in triple agonists increases energy expenditure and lipid oxidation, contributing to weight loss without causing hyperglycemia when combined with GLP-1 and GIP.

The addition of glucagon receptor activation in triple agonists helps burn more energy and fat, contributing to weight loss without raising blood sugar, thanks to the balancing effects of GLP-1 and GIP.

Bariatric surgery significantly reduces the incidence of overall cancer and obesity-related cancers, with a more pronounced effect in women.

Bariatric surgery is a highly effective intervention for reducing cancer risk in people with severe obesity, particularly women. It offers a significant reduction in overall and obesity-related cancers compared to non-surgical controls.

Physical activity reduces cancer risk independently of its effect on body weight, through mechanisms like improved immune regulation and reduced oxidative stress.

Regular physical activity lowers your risk of breast and colon cancer, even if you don't lose weight. It works through mechanisms like better immune function and less inflammation.

In older adults (55-70 years), long-term lifestyle interventions for weight loss in prediabetes result in greater sustained weight loss but inferior preservation of fat-free mass and bone mineral content compared to younger adults (25-45 years).

If you are over 55 and losing weight, expect to lose more muscle and bone than a younger person would for the same amount of weight lost. To counter this, you must prioritize resistance training and adequate protein intake, as standard lifestyle interventions alone may not preserve lean mass effectively in this age group.

Men tend to lose more absolute weight than women when undergoing non-pharmacological lifestyle interventions (diet and exercise), although the difference is small.

If you are a woman doing lifestyle changes (diet/exercise), you might lose slightly less weight than a man on the same plan. This is normal. Focus on consistency, as women often have better long-term weight maintenance success.