Browse the evidence

Low-carbohydrate diets improve triglyceride levels and HDL cholesterol more effectively than low-fat diets, but result in less reduction (or potentially less favorable changes) in LDL and Total Cholesterol compared to low-fat diets.

If you have high triglycerides or low HDL, a low-carbohydrate diet is likely superior to a low-fat diet for improving your lipid profile. However, if your LDL cholesterol is a primary concern, note that low-fat diets may lower LDL more effectively. Monitor your Total/HDL ratio, which remained similar between diets in this analysis.

Low-carbohydrate/high-protein diets improve cardiovascular risk markers (HDL, Triglycerides, Systolic BP) more effectively than low-fat diets, despite potentially increasing LDL and Total Cholesterol.

When switching to a low-carb diet, monitor your lipids. You may see an increase in LDL and Total Cholesterol, but you will likely see a beneficial increase in HDL ('good') cholesterol, a drop in Triglycerides, and a slight drop in blood pressure. These changes often offset the LDL increase, resulting in a net positive or neutral cardiovascular risk profile compared to low-fat diets.

High-protein diets, particularly those with a high Glycemic Index, can increase LDL cholesterol levels, negating cardiovascular benefits despite potential fat loss.

Be cautious with high-protein diets that also rely on high-GI carbohydrates (like white rice/pasta with meat). This combination may raise your LDL cholesterol. Opt for high-protein diets paired with low-GI carbohydrates to avoid this risk.

Higher exercise capacity (measured in METs) is inversely and independently associated with all-cause mortality in older men (aged 65-92), with significant survival benefits achieved at capacities above 5 METs.

For older men, focusing on improving physical fitness (measured as METs) is one of the most powerful ways to extend life. You do not need to be an elite athlete; achieving a moderate fitness level (above 5 METs, roughly equivalent to brisk walking or light jogging) provides significant survival benefits. If you are currently unfit, improving your fitness through regular activity can lower your mortality risk by approximately 35% compared to staying unfit.

Genetic similarity strongly predicts the magnitude of abdominal visceral fat loss in response to negative energy balance and exercise.

If you are struggling to lose belly fat despite exercise and diet, your genetics may dictate a slower rate of visceral fat mobilization compared to others. However, this specific exercise protocol (moderate intensity, constant intake) is proven to reduce visceral fat significantly regardless of genetic background.

Very-low-calorie diets (VLCDs, ~420 kcal/day) produce significantly greater short-term weight loss (approx. 21 kg) compared to moderate caloric restriction (1,200 kcal/day, approx. 12 kg) over 26 weeks, but this advantage is entirely lost by 78 weeks due to rapid weight regain in the VLCD group.

While a very low-calorie diet (around 400-500 calories) will help you drop weight much faster than a standard 1,200-calorie diet in the first 4 months, it does not help you keep it off. In fact, people on the extreme diet regained most of their weight by the end of the year, ending up with less net loss than those who lost weight more slowly. Focus on a sustainable deficit and maintenance strategies rather than extreme speed.

MCT consumption increases postprandial energy expenditure and fat oxidation in the short term (2 days), but this effect diminishes after 28 days of continuous consumption.

You might notice a slight boost in calorie burning when you first start using MCT oil, but this effect fades after a few weeks. Don't rely on it for long-term weight management. It's a minor tool, not a primary strategy.

Very Low-Calorie Diets (VLCDs) defined as ≤800 kcal/day with high-biologic-value protein produce significantly greater short-term weight loss (1.5-2.5 kg/week) compared to standard low-calorie diets (LCDs, 1200 kcal/day), but long-term weight maintenance is poor and not superior to LCDs when behavioral therapy is included.

If you are severely obese (BMI >30) and have failed standard diets, a VLCD (≤800 kcal/day) with high protein can help you lose weight much faster (approx. 20kg in 12-16 weeks) than a standard 1200 kcal diet. However, you must combine this with behavioral therapy and exercise, as VLCDs alone do not prevent weight regain long-term. This must be done under medical supervision to manage risks like gallstones.

In nonobese middle-aged adults, achieving equivalent fat loss through either calorie restriction or exercise yields similar improvements in major coronary heart disease risk factors, including LDL-cholesterol, insulin resistance, and inflammation.

If you are overweight but not obese, you can improve your heart disease risk by either eating 20% less or exercising enough to burn 20% more calories daily. The key is losing fat; it doesn't matter much which method you use to get there, as long as you achieve the fat loss.

Intensive weight loss interventions (behavioral programs, pharmacotherapy, or surgery) significantly improve biomarkers of nonalcoholic fatty liver disease (NAFLD), including liver enzymes (ALT, AST), steatosis, and disease activity scores, but do not significantly reverse histologic liver fibrosis in the short-to-medium term.

If you have NAFLD, intensive weight loss is the most effective way to improve liver health markers like enzymes and fat content. Focus on programs that achieve significant weight loss (via diet, exercise, medication, or surgery) rather than just changing diet composition without losing weight. Be aware that while liver fat and inflammation improve, existing scarring (fibrosis) may not reverse in the short term (6 months), so consistency is key.

Ramadan fasting induces a transient reduction in body weight and fat mass in healthy non-athlete adults, with effects being more pronounced in individuals with overweight or obesity and reversing within 2-5 weeks post-fast.

If you fast during Ramadan, expect to lose about 1.3 kg of weight and some fat by the end of the month, especially if you are overweight. This loss is not permanent; you will likely regain the weight within a month after fasting ends. To maintain any fat loss, you must manage your eating habits during the non-fasting hours (iftar/suhoor) to avoid overcompensating.

Ramadan fasting significantly reduces fat percentage and absolute fat mass in overweight/obese individuals, but not in those with normal weight, while also causing a smaller, transient loss of fat-free mass.

If you are overweight, Ramadan fasting will likely reduce your body fat percentage. If you are normal weight, your body fat percentage may not change significantly. In all cases, you will lose some lean mass, but you will lose more fat than lean mass. This benefit is temporary and reverses after the fast.

Intensive caloric restriction (330 kcal/day) rapidly and significantly lowers fasting plasma glucose in obese NIDDM patients, with maximal glycemic improvement occurring within 10 days, largely independent of the total amount of weight lost.

For obese individuals with type 2 diabetes, rapidly lowering carbohydrate and total caloric intake can normalize blood sugar levels much faster than weight loss itself. This suggests that the metabolic benefit comes from reducing the liver's glucose production and improving insulin sensitivity, not just from losing fat mass. Medical supervision is required for such extreme restriction.

Isocaloric refeeding after a Very Low Caloric Diet maintains significantly lower fasting plasma glucose levels compared to pre-diet baselines, even after discontinuation of antidiabetic medications, although glucose levels rise from the nadir achieved during the diet.

Even after stopping a strict low-calorie diet and returning to normal eating, people with type 2 diabetes often maintain better blood sugar control than they had before starting the diet. This suggests that a period of intensive dietary intervention can have long-lasting metabolic benefits, even if weight regain occurs.

The rapid improvement in fasting plasma glucose induced by caloric restriction is closely correlated with a reduction in basal hepatic glucose output (HGO), suggesting that restraining HGO is a major mechanism of action.

Reducing caloric intake works partly by telling the liver to stop producing so much sugar. This metabolic shift happens quickly, often before significant fat loss occurs.

Dietary weight loss via a hypocaloric DASH-based diet significantly reduces sympathetic nervous system (SNS) activity (norepinephrine spillover and muscle sympathetic nerve activity) and improves cardiac baroreflex sensitivity in subjects with metabolic syndrome.

For individuals with metabolic syndrome, a structured weight loss program using a modified DASH diet (moderate fat, higher protein, low sodium) for 12 weeks can significantly reduce harmful sympathetic nervous system activity and improve heart health markers. This approach targets the root metabolic drivers (insulin resistance and leptin levels) rather than just weight, offering cardiovascular protection beyond simple fat loss.

Insulin-resistant subjects experience a significant reduction in whole-body norepinephrine spillover after weight loss, whereas insulin-sensitive subjects do not, despite similar weight loss amounts.

If you have metabolic syndrome and are insulin resistant, weight loss is particularly effective at calming your nervous system's stress response. If you are already insulin sensitive, weight loss still helps other metabolic markers, but may not lower sympathetic nerve activity as dramatically.

Very-low-calorie diets (VLCDs, 400-800 kcal/d) produce significantly greater initial weight loss than low-calorie diets (LCDs, 800-1200 kcal/d), but long-term weight maintenance success is determined by active follow-up (behavioral therapy, nutrition education, exercise) rather than the initial diet intensity.

To use a VLCD effectively, do not just rely on the low calories. You must pair the 400-800 kcal diet with active behavioral therapy, nutritional education, and exercise. This combination is what leads to sustained weight loss, whereas VLCD alone often fails long-term.

The 5:2 diet improves liver stiffness (a marker of fibrosis/inflammation) and reduces LDL cholesterol, whereas LCHF does not improve liver stiffness and may increase LDL.

If you have high cholesterol or heart disease risk, the 5:2 diet might be a better choice than LCHF because it lowers LDL and improves liver stiffness. LCHF reduces liver fat just as well but may not help with stiffness or cholesterol as much.

Intermittent fasting significantly increases adiponectin and decreases leptin levels, which may contribute to improved insulin sensitivity independent of significant fat mass loss.

Fasting may improve your metabolic health markers (like adiponectin) even if the scale doesn't move much, suggesting benefits beyond just weight loss.

A ketogenic diet is more effective than low-fat diets for improving glycemic control (HbA1c and HOMA-IR) in patients with type 2 diabetes, but shows comparable effects in non-diabetic patients.

If you have type 2 diabetes and are overweight, switching to a ketogenic diet (very low carb, high fat) is likely to improve your blood sugar control more effectively than a standard low-fat diet. If you do not have diabetes, the blood sugar benefits are similar to low-fat diets, though weight loss may still be superior.

Intermittent energy restriction (IER) significantly reduces fasting insulin levels compared to continuous energy restriction (CER), although the clinical relevance is uncertain.

IER may offer a slight advantage in lowering fasting insulin compared to daily restriction, which could be beneficial for metabolic health. However, since weight loss is the same, do not expect dramatic changes in body composition solely from this hormonal shift.

Islamic fasting during Ramadan results in a statistically significant but small average weight loss (approx. 1.24 kg) during the fasting month, which is almost entirely regained within weeks after Ramadan ends, resulting in negligible long-term weight change.

If you are observing Ramadan, expect to lose about 1-1.5 kg during the month, but do not rely on this for long-term weight management. The weight will likely return after Eid unless you actively maintain the dietary and activity habits you formed during the fast. Focus on maintaining the reduced meal frequency and healthy food choices post-Ramadan to make the weight loss stick.

Physical exercise alone produces modest weight loss (approx. 2 kg) but significantly improves obesity-associated risk factors and abdominal fat, and is critical for long-term weight maintenance.

Aim for at least 150 minutes of moderate-to-high intensity exercise per week (e.g., brisk walking, cycling). While this will only result in about 2-3 kg of weight loss on its own, it is essential for improving your health risks and keeping the weight off after you lose it through diet.