Browse the evidence

Metabolic Flux Analysis (MFA) using stable isotopes is a key technique for elucidating how dietary components affect lipoprotein metabolism and insulin resistance.

Researchers use stable isotope tracing to measure exactly how the body processes dietary fats and sugars. This helps identify specific metabolic bottlenecks that contribute to diseases like diabetes and heart disease.

Metabolic adaptation (suppressed resting metabolic rate beyond what is predicted by body composition changes) persists for at least 6 years after massive weight loss, acting as a persistent biological barrier to weight maintenance.

If you have lost a significant amount of weight, your body will likely fight to regain it by lowering your metabolic rate, even years later. This is not a failure of willpower but a biological response. To maintain your weight, you must accept that your energy requirements are now lower than they were before you were heavier, and you may need to be more vigilant about energy balance than someone who has never been obese.

When total energy deficit is strictly matched, adding structured aerobic exercise to caloric restriction provides no additional benefit for fat mass loss or abdominal fat distribution compared to caloric restriction alone.

If your goal is purely fat loss and you are willing to restrict calories, adding exercise will not make you lose more fat than dieting alone, provided the total calorie deficit is the same. However, exercise is still valuable for improving cardiovascular health and aerobic fitness, which are independent benefits of weight loss. Do not feel guilty if you skip the gym; your fat loss progress depends on your net energy balance, not the source of the deficit.

Higher intake of total and saturated fat is associated with an increased risk of type 2 diabetes, but this association is not independent of Body Mass Index (BMI) and disappears after adjusting for BMI.

While high fat intake is linked to higher diabetes risk in unadjusted analyses, this link disappears when you account for body weight. This suggests that managing your weight (BMI) is the key factor, not necessarily cutting out all dietary fat. Focus on maintaining a healthy weight rather than fearing fat itself.

Obese women exhibit significantly higher total free-living energy expenditure than lean women, contradicting the hypothesis that obesity is caused by reduced energy expenditure.

If you are obese, your body likely burns more calories than a lean person of similar height due to the energy cost of moving and maintaining larger mass (both fat and fat-free mass). The idea that you have a 'slow metabolism' causing obesity is scientifically unsupported by this study. The issue is likely that you are consuming more energy than you realize, not that you are burning less.

When adjusted for fat-free mass, basal metabolic rate and energy expenditure on thermogenesis plus activity are identical in lean and obese women.

Your basal metabolic rate is determined by your fat-free mass (muscle, organs, bone), not by your fat mass. Obese individuals have higher total BMR simply because they have more fat-free mass to support, not because their metabolism is inherently 'fast' or 'slow' per unit of tissue.

Resting metabolic rate (RMR) is significantly influenced by familial factors, with a heritability estimate of approximately 40-70%, independent of body composition and lifestyle factors.

Your resting metabolic rate is partly determined by your genetics, independent of your weight. This doesn't mean you can't lose weight, but it means you may need to be more precise with your calorie intake and activity levels than someone with a different genetic baseline. Focus on building lean muscle mass, which increases RMR, and use metabolic testing if available to tailor your diet accurately.

BCAA supplementation does not improve exercise performance, contradicting the hypothesis that BCAAs serve as a significant fuel source during exercise.

Do not buy BCAA supplements expecting them to boost your workout performance. The evidence shows they do not enhance performance when used as fuel.

Acute overfeeding leading to weight gain increases COL6A3 mRNA expression in human adipose tissue.

Gaining weight through overfeeding increases the expression of COL6A3, a protein associated with fat tissue fibrosis and inflammation. This suggests that even short-term weight gain can have structural impacts on fat tissue. Maintaining a stable weight may help avoid these structural changes.

High-protein diets do not enhance weight or fat loss compared to lower-protein diets when total energy intake is strictly fixed.

If you are counting calories strictly, increasing protein won't make you lose more weight than a lower-protein diet with the same calories. The benefit of protein comes from helping you eat less naturally, not from burning more fat directly.

The obesity epidemic is primarily driven by changes in the caloric quantity and quality of the food supply, specifically the industrialization of cheap, highly processed foods with supernormal appetitive properties, rather than by specific macronutrients like protein, fat, or carbohydrates.

Focus on the overall food environment rather than isolating single nutrients. The rise in obesity is linked to the availability of cheap, highly processed, convenient foods that are engineered to be overconsumed. Reducing reliance on these foods and increasing home-prepared meals may help mitigate intake.

SGLT2 inhibitors produce significantly less weight loss than predicted by urinary glucose excretion because of compensatory hyperphagia (increased energy intake).

If you are taking an SGLT2 inhibitor (like Jardiance or Farxiga), expect about 2-3 kg of weight loss, not the 7 kg you might calculate based on urine sugar loss. Your body will likely increase your hunger to compensate for the calories lost in urine. To maximize weight loss, you must actively manage your appetite and food intake, as the drug alone will not overcome this biological compensation.

Obese individuals have less brown adipose tissue mass and activity than lean individuals, which may contribute to obesity susceptibility.

Obese individuals tend to have less active brown fat, but it is unclear if restoring it would lead to weight loss.

Spontaneous long-term weight gain triggers a metabolic adaptation where increases in 24-hour energy expenditure and fat oxidation are overcompensatory (greater than predicted by changes in body composition), acting to oppose further weight gain.

Your body does try to defend its weight when you gain it, by burning slightly more calories and fat. However, this defense is very weak—roughly equivalent to the calories in half an apple. This means that while your body is trying to help, it is easily overwhelmed by small increases in food intake. Understanding this helps explain why weight gain is easy to sustain and why willpower alone is difficult; the biological 'brakes' are weak.

Linoleic acid has a long half-life in the body (approximately two years), meaning that reducing intake takes years to significantly lower tissue levels.

Be patient when reducing seed oils. It can take up to six years to significantly replace body stores of linoleic acid with healthier fats.

Nutritional stunting (chronic early-life undernutrition) causes long-term physiological adaptations—including lower resting energy expenditure, reduced fat oxidation, and impaired food intake regulation—that increase susceptibility to obesity when caloric intake increases.

If you were stunted as a child, your body may be biologically programmed to store fat more efficiently and burn less energy than someone who was well-nourished. Standard 'eat less, move more' advice may be less effective because your metabolic rate and fat oxidation are lower. Focus on nutrient-dense foods and strength training to preserve muscle mass, rather than severe caloric restriction, which your body may resist more strongly.

Higher BMI (specifically >40 kg/m2) is associated with a significantly increased risk of severe vision loss and more severe papilledema in IIH patients.

If you have IIH, maintaining a lower BMI is crucial to protect your vision. A BMI over 40 kg/m2 significantly increases your risk of severe vision loss. Prioritize weight management to mitigate this risk.

In healthy young men, overfeeding by ~1,000 kcal/day for 21 days does not trigger a significant adaptive increase in energy expenditure (other than obligatory thermic effect), resulting in 85-90% of excess energy being stored as fat and protein.

If you are a healthy young man, eating 1,000 extra calories a day for three weeks will not significantly boost your metabolism to burn off those calories. Instead, your body will store about 85-90% of that excess energy as fat and protein. You might naturally eat less later, but during the overfeeding period, you will gain weight because your energy expenditure does not increase enough to match the intake.

Matching the total energy expenditure of exercise bouts reveals that high-intensity aerobic exercise does not result in greater 24-hour energy expenditure or fat oxidation compared to low-intensity exercise.

If your goal is fat loss, focus on the total calories you burn, not just the intensity. This study shows that doing 400 calories of low-intensity cycling burns just as much fat over 24 hours as doing 400 calories of high-intensity cycling. You can choose the intensity that you can sustain consistently without injury or burnout. High intensity is not 'better' for fat oxidation if the total work is the same.

The doubly labeled water method slightly underestimates energy expenditure in heavier and fatter subjects compared to respiratory gas exchange, likely due to larger sequestration of isotopes in fat synthesis.

If you are using doubly labeled water to measure your energy needs, be aware that the device may slightly underestimate your true expenditure if you have a high body fat percentage. This is likely due to isotopes being sequestered in fat synthesis. For leaner individuals, the method is highly accurate.

The beta-3 adrenoceptor agonist TAK-677 fails to produce significant metabolic effects (fat loss or oxidation) in obese humans, despite increasing energy expenditure slightly at the highest dose.

TAK-677, a beta-3 agonist tested in obese individuals, did not result in fat loss or changes in body composition, despite a slight increase in energy expenditure at the highest dose. This suggests that beta-3 agonists are not a viable standalone treatment for obesity in humans, likely due to low receptor density or bioavailability issues.

Intermittent Energy Restriction (IER), including intermittent fasting and time-restricted eating, does not provide clear incremental benefit over Continuous Energy Restriction (CER) for weight loss or cardiometabolic health in humans.

Intermittent fasting or time-restricted eating is not superior to simply eating fewer calories every day for weight loss or heart health. If you prefer fasting, it may help you restrict calories, but it offers no extra metabolic benefit over consistent daily calorie control. Choose the approach that fits your lifestyle and allows you to maintain a healthy diet.

Physical activity levels (measured by PAL and activity monitors) remain stable between young adulthood (20-34 years) and middle age (60-74 years), with a significant decline only occurring in nonagenarians (90+ years).

You do not need to accept a gradual decline in activity as you move from your 20s to your 60s. This research shows that physical activity levels can be maintained throughout middle age. The significant drop in activity only occurs in the 90s. Focus on maintaining your current activity habits, as the biological drive to move does not necessarily fade until very late in life.

Intensive lifestyle intervention (ILI) increases the risk of frailty fractures and negatively impacts bone mineral density and lean body mass in adults with overweight/obesity and type 2 diabetes.

Be aware that significant weight loss can lead to some loss of bone density and a higher risk of fractures. Discuss strategies to protect your bones, such as ensuring adequate calcium/vitamin D intake and incorporating resistance training, with your healthcare provider while pursuing weight loss.