Browse the evidence

The guidelines mostly agree, although there are slight differences in their recommendations.

Practitioners should be aware of both the consensus and differences in the guidelines.

A 6-month dietary intervention producing a 500 kcal/day energy deficit yields similar weight loss outcomes regardless of an individual's high or low genetic predisposition to higher BMI, as measured by genome-wide polygenic scores.

If you are overweight or mildly obese, a standard dietary intervention creating a 500 kcal/day deficit will likely help you lose weight, regardless of your genetic risk for obesity. You do not need a specialized or 'genetic' diet to succeed; standard caloric restriction is effective for everyone in this range.

Intermittent Fasting (IF) is defined as repetitive fasting periods lasting up to 48 hours each, including Time-Restricted Eating (TRE) and Alternate-Day Fasting (ADF).

Intermittent Fasting means you fast repeatedly, with each fast lasting no more than 48 hours. This includes popular methods like Time-Restricted Eating (eating within a daily window) and Alternate-Day Fasting. You do not need to restrict calories during eating windows if you choose TRE.

Time-Restricted Eating (TRE) is defined as restricting food and caloric beverage intake to a specific daily period, resulting in a fasting window of at least 14 hours, with no explicit limit on energy intake during eating hours.

Practice Time-Restricted Eating by limiting your daily food and calorie-containing drink consumption to a window of at least 14 hours. You do not need to restrict the amount of food you eat during this window.

Weight loss interventions trigger physiological countermeasures, specifically adaptive thermogenesis (reduced resting energy expenditure) and increased appetite drive, which persist long-term and make weight maintenance difficult.

Understand that after losing weight, your body will biologically fight to regain it by lowering your calorie burn and increasing hunger. This is a normal physiological response, not a personal failure. Long-term maintenance requires strategies that account for these biological changes, such as higher protein intake or resistance training, rather than relying on willpower alone.

Long-term consumption of sugar-sweetened beverages (SSBs) is positively associated with increased total and cardiovascular disease (CVD) mortality in a graded, dose-dependent manner.

Limit sugar-sweetened beverages to less than one serving per month to minimize mortality risk. Each additional daily serving increases the risk of death by approximately 7%, primarily due to cardiovascular causes. Replace SSBs with water or unsweetened alternatives.

Sustained moderate caloric restriction (average 11.9% reduction over 24 months) improves aging-related biomarkers and metabolic health without causing adverse psychological or behavioral outcomes in healthy, non-obese adults.

To improve aging biomarkers and metabolic health, aim for a moderate, sustained reduction in calorie intake (around 10-12%) over a long period (e.g., 2 years). This should be done with professional guidance, using behavioral strategies to maintain adherence, and ensuring you take a multivitamin and calcium supplement to prevent deficiencies. This approach is safe and effective even for non-obese individuals.

Total daily energy expenditure (TDEE) in healthy, free-living, non-athlete individuals is primarily composed of resting energy expenditure (approx. 60%), physical activity energy expenditure (approx. 30%), and the thermic effect of food (approx. 10%).

To understand your daily energy needs, recognize that most energy (60%) is used just to keep your body running at rest, about 30% goes to movement, and 10% is used to digest food. This breakdown helps in estimating caloric requirements for health maintenance.

Physical activity energy expenditure (PAEE) is highly variable among individuals and can range from almost none in bedridden individuals to approximately 50% of TDEE in highly active individuals.

Your physical activity level is the most variable component of your daily energy expenditure. Increasing your movement can significantly increase your total energy needs.

Current pharmacological treatments for obesity, including incretin-based therapies (semaglutide, tirzepatide), result in significant skeletal muscle loss (approx. 7-10% of lean mass) alongside fat loss.

If you are using GLP-1 medications, expect to lose some muscle. You must actively combat this by eating enough protein and doing resistance training to preserve your metabolic engine.

Among patients with type 2 diabetes in placebo-controlled trials, baseline BMI has significantly increased over time (rising by ~0.70 kg/m² per decade), indicating a growing prevalence of obesity and inadequate management of weight despite improved glycemic control.

If you have Type 2 Diabetes, your weight is likely increasing even if your blood sugar is controlled. This meta-analysis of over 260,000 patients shows that baseline BMI has risen by 0.7 kg/m² every decade. You cannot ignore weight management; it is becoming harder, not easier, to maintain a healthy weight with current standard care. Focus on energy balance (diet and activity) as rigorously as you focus on glucose numbers.

Metabolic bariatric surgery is the most effective treatment for obesity across all BMI classes, offering durable weight loss and improvement in comorbidities.

For eligible patients (BMI ≥35, or 30-34.9 with failed lifestyle/pharma), metabolic bariatric surgery (sleeve or bypass) is the most effective treatment for durable weight loss and comorbidity improvement. It is recommended for BMI ≥35 regardless of comorbidities.

Intermittent fasting (IMF) and daily caloric restriction (DCR) produce equivalent weight loss when matched for energy deficit and delivered with guideline-based behavioral support and physical activity prescriptions.

To lose weight effectively, you can choose either daily calorie restriction or intermittent fasting, but the key is consistency and support. Ensure your total weekly energy deficit is similar regardless of the method. Crucially, engage in a structured behavioral support program that includes regular check-ins, goal setting, and physical activity (aiming for 300 minutes of moderate exercise per week). This structured approach is more important than the specific timing of your meals for long-term success.

Cardiovascular disease is the primary cause of death associated with high BMI, accounting for more than two-thirds of high-BMI-related deaths.

Heart disease is the biggest killer linked to high body weight. Keeping your BMI in the 20-25 range is one of the most effective ways to protect your heart.

High body-mass index (BMI) is a significant metabolic risk factor with increasing exposure rates (1.8% annually) and a 15.7% rise in age-standardized DALY rates from 2000 to 2021.

High BMI is a significant metabolic risk factor with increasing exposure rates. Addressing high BMI is crucial for long-term health.

Waist circumference is a superior and necessary clinical metric for assessing cardiometabolic risk compared to BMI alone, as it identifies visceral adiposity and high-risk phenotypes that BMI misses.

Stop relying solely on your weight or BMI. Measure your waist circumference. If it is high (≥88 cm for women, ≥102 cm for men), you are at higher risk for heart disease and diabetes, even if your weight is 'normal'. Use this measurement to guide lifestyle changes.

Obesity and insulin resistance are core drivers of NAFLD, leading to liver accumulation of triglycerides and free fatty acids.

Managing body weight and insulin sensitivity is the most critical step in preventing and treating NAFLD, as these conditions directly cause fat accumulation in the liver.

Short-chain fatty acids (SCFAs) like butyrate, produced by gut bacteria from dietary fiber, have anti-inflammatory, anti-cancer, and barrier-integrity functions, and their production declines with age and frailty.

Eat enough dietary fiber (fruits, vegetables, whole grains) to feed your gut bacteria. They will produce SCFAs like butyrate, which protect your gut lining, reduce inflammation, and support metabolic health. This is especially important as you age.

Ketone bodies (KBs) serve as an efficient energy source that bypasses glycolysis, promoting mitochondrial oxidative metabolism and reducing oxidative stress.

Your brain can run efficiently on ketone bodies produced by the ketogenic diet. These molecules enter the Krebs cycle directly, bypassing the slower glycolytic pathway, which enhances mitochondrial energy production and reduces oxidative stress. This metabolic shift is central to the diet's benefits for neurological and metabolic health.

Physical inactivity is a major global health risk, ranking as the fourth leading cause of mortality and contributing to 3.2 million deaths annually, primarily through cardiovascular disease, diabetes, hypertension, and certain cancers.

Recognize that physical inactivity is a critical health risk, comparable to smoking or obesity. Prioritize increasing daily movement to reduce the risk of cardiovascular disease, diabetes, and hypertension. In Arab countries, be aware that cultural and gender-specific barriers may exist, requiring tailored solutions to overcome them.

Mitochondrial impairment accelerates epigenetic aging, while enhancing mitochondrial biogenesis slows it, establishing a direct link between mitochondrial function and the rate of epigenetic aging.

Mitochondrial health is a key driver of epigenetic aging. Impairing mitochondria accelerates the epigenetic clock, while boosting mitochondrial biogenesis slows it. This suggests that interventions supporting mitochondrial function (like exercise or specific nutrients) may slow epigenetic aging, independent of DNA repair or telomere length.

The doubly labelled water (DLW) method is the gold standard for measuring total energy expenditure in free-living humans because it accurately captures activity energy expenditure without interfering with subject behavior.

If you need to know your true energy expenditure in daily life, self-reports and most wearables are unreliable. The doubly labelled water method is the only validated way to measure this accurately without restricting your normal activities, though it is primarily a research tool due to cost and complexity.

Fat-free mass-adjusted total and basal energy expenditure peaks at approximately 50% above adult levels around 1 year of age, then declines to adult baseline levels by age 20, remaining stable through age 60 before declining in older adults.

Your body's energy needs change predictably as you age. You burn significantly more energy relative to your size as a toddler (peaking around age 1) than as an adult. As you age from 20 to 60, your metabolic rate (adjusted for size) stabilizes. After 60, it declines. Do not assume your metabolic rate is constant or scales linearly with your weight; use age- and size-specific estimates for nutritional planning rather than simple weight-based ratios.

Low-carbohydrate diets do not increase total energy expenditure (TEE) compared to high-carbohydrate diets when analyzed according to pre-registered protocols and accounting for energy conservation laws.

If you are trying to lose weight, switching to a low-carbohydrate diet will not give you a metabolic advantage in terms of burning more calories at rest or during activity compared to a high-carbohydrate diet, provided you eat the same number of calories. Focus on maintaining a caloric deficit rather than macronutrient composition for energy expenditure benefits.