Browse the evidence

Intermittent Fasting improves metabolic health markers, including insulin sensitivity, lipid profiles (reduced triglycerides and LDL), and blood pressure, independent of weight loss magnitude, through mechanisms involving ketone body production and hormonal regulation.

Beyond weight loss, IER can improve your blood lipids and blood pressure. This happens partly because your body switches to burning fat for fuel (ketones) during fasting periods, which improves insulin sensitivity and reduces inflammation. You do not need to lose a massive amount of weight to see these metabolic benefits.

Progressive weight loss triggers adaptive physiological reductions in energy expenditure, specifically a drop in Resting Metabolic Rate (RMR) at ≥5% weight loss and a reduction in Exercise-Induced Energy Expenditure (EIEE) at ≥10% weight loss, which creates metabolic resistance to further weight loss.

If you are losing weight and then stall, do not assume you have failed or are eating too much. Your body is biologically reducing its energy needs (Resting Metabolic Rate drops at 5% loss, Exercise Efficiency increases at 10% loss) to conserve energy. This is a normal survival mechanism. To continue, you must adjust your expectations, potentially increasing physical activity or slightly adjusting intake, knowing this is a temporary physiological hurdle, not a permanent failure.

Low-carbohydrate diets produce significantly greater short-term weight loss (3-8 months) in obese individuals compared to non-carbohydrate-restricted diets, but this advantage disappears in the long term (10-30 months).

If you are obese, a low-carb diet will help you lose more weight than a standard balanced diet for the first 6-8 months. However, do not expect this advantage to last beyond a year; after 10 months, your weight loss will likely match that of someone on a balanced diet. The key benefit of LC diets in the long run is not weight loss, but improved lipid profiles (lower triglycerides, higher HDL).

The 5:2 intermittent energy restriction diet produces weight loss equivalent to standard brief lifestyle advice over 12 months, with no adverse effects on physical activity or macronutrient intake.

Try the 5:2 diet by restricting calories to 500 (women) or 600 (men) on two non-consecutive days a week. Eat normally on the other five days. Expect modest weight loss (around 2kg) over a year, similar to standard diet advice. If you struggle with hunger, know that it often decreases over time, and consider joining a support group to help you stick with it initially.

Adding weekly group support to the 5:2 diet improves short-term adherence and weight loss (at 6 weeks), but this advantage diminishes and becomes statistically non-significant by 12 months.

If you start the 5:2 diet, try to get some form of support for the first 6 weeks, such as a group session or a buddy system. This will help you lose more weight initially. However, be aware that this advantage may fade after a year, so focus on building sustainable habits rather than relying solely on support.

Performing 250 minutes per week of self-paced aerobic exercise yields modest weight loss regardless of whether the exercise is performed in the morning (06:00–09:00) or evening (16:00–19:00).

If you want to lose weight, focus on getting 250 minutes of moderate aerobic exercise per week. It does not matter if you do it in the morning or the evening; the weight loss results are the same. Choose the time that fits your schedule best to ensure you stick with it.

Fatmax training does not significantly increase maximal oxygen consumption (VO2max) compared to other forms of exercise, but it does improve it in sedentary obese individuals.

Fatmax training improves cardiovascular fitness (VO2max) in obese, sedentary individuals, though the gains are modest. It is a safe starting point for those who cannot tolerate high-intensity exercise.

In healthy, normal-weight young adults, 5:2 intermittent energy restriction (IER) produces equivalent weight loss and postprandial metabolic responses to continuous energy restriction (CER), but yields superior improvements in fasting blood glucose and fasting subjective appetite scores.

If you are a healthy, normal-weight individual looking to lose weight, 5:2 intermittent fasting is just as effective as eating slightly less every day. You will lose the same amount of weight and see similar improvements in how your body handles food after meals. However, 5:2 fasting may offer a slight edge in lowering your fasting blood sugar and reducing hunger feelings when you wake up, which might help with long-term compliance for some people.

An 8-week sulfur amino acid restriction (SAAR) diet (~2 g/day) in humans with overweight or obesity produces significantly greater weight loss (~20% greater) compared to a control diet (~5.6 g/day), despite maintaining similar resting metabolic rates.

To lose more weight than standard dietary restriction, try reducing sulfur amino acids (methionine and cysteine) to about 2 grams per day for 8 weeks. This can be done by eating a plant-based diet and avoiding high-sulfur supplements or specific high-sulfur foods, while allowing one flexible meal a week to maintain social life. Expect roughly 20% more weight loss than a standard control diet, even if your resting metabolism doesn't change.

Sulfur amino acid restriction (SAAR) significantly decreases serum leptin levels and increases plasma ketone bodies (beta-hydroxybutyrate and acetoacetate) compared to a control diet, indicating a shift in metabolic fuel usage.

Reducing sulfur amino acids lowers leptin (a hormone that signals fat stores to the brain) and increases ketones. This suggests your body is switching to burning fat for fuel more efficiently, which may help sustain weight loss.

Metabolic adaptation (a lower-than-predicted resting metabolic rate after weight loss) significantly increases the time required to reach specific weight loss goals, independent of dietary adherence.

If you are strictly following a calorie deficit but your weight loss has stalled or slowed significantly, it may be due to metabolic adaptation (a drop in your resting metabolic rate). This is a biological defense mechanism, not a personal failure. Adjusting expectations regarding the timeline, rather than just increasing restriction, is necessary.

VLCD intervention significantly increases Sex-Hormone-Binding Globulin (SHBG) and reduces fasting blood glucose in obese women with PCOS, whereas moderate energy deficit does not significantly alter these specific metabolic markers over 8 weeks.

VLCDs offer a metabolic advantage over moderate dieting for PCOS patients by significantly boosting SHBG and lowering fasting glucose. This suggests VLCD may be necessary to reverse the underlying insulin resistance driving hyperandrogenism in some patients.

Smartphone-only apps for weight management produce a modest but statistically significant reduction in body weight and BMI in adults with overweight or obesity, but this effect is limited to a 4-6 month window and diminishes thereafter due to lack of personalization.

Use a smartphone app for weight loss if you can commit to using it daily for 4-6 months. Expect modest results (SMD -0.33) and be prepared for weight regain if you stop using it. To maximize success, choose an app that offers some level of personalization or feedback, as generic apps have high dropout rates. This is not a long-term solution without human support or advanced AI customization.

Manipulating energy density does not significantly alter the total amount of food consumed (in grams), meaning volume intake remains constant.

Do not worry about shrinking your portions. When you lower the energy density of your food (e.g., by adding vegetables), you can eat the same amount of food by weight. This helps maintain satiety and makes the diet easier to follow long-term.

Intermittent fasting (IF) significantly reduces body weight, BMI, body fat mass, LDL cholesterol, and triglycerides in Chinese adults compared to control groups, but does not significantly reduce waist circumference, total cholesterol, HDL cholesterol, fasting glucose, or blood pressure.

If you are Chinese and looking to lose weight or improve lipid profiles, intermittent fasting (like 16:8 TRE or 5:2) is an effective strategy. Expect a modest weight loss (around 2kg) and improvements in LDL and triglycerides. However, do not expect IF to significantly lower your blood pressure or fasting glucose on its own. Adherence may be challenging due to typical eating patterns, so choose a protocol that fits your lifestyle.

Fasting-based strategies (FBS) produce slightly greater short-term weight loss and fat mass reduction compared to continuous caloric restriction (CCR) in obese adults, but these differences are not clinically significant and disappear in long-term interventions (>6 months).

If your goal is weight loss, fasting strategies (like time-restricted eating) might help you lose a bit more weight and fat in the first few months compared to simply counting calories every day. However, this advantage is small (less than 1 kg) and disappears after 6 months. Since both methods result in similar long-term weight loss, choose the approach that fits your lifestyle and is easier for you to maintain consistently.

Fasting-based strategies improve insulin sensitivity (reduced fasting insulin and HOMA-IR) in the short term compared to continuous caloric restriction, but this benefit is not sustained in long-term outcomes for fasting glucose.

If you are obese, trying fasting strategies (like time-restricted eating) may help improve your insulin sensitivity in the first few months compared to just counting calories. This is measured by lower fasting insulin levels. However, this doesn't necessarily mean you will lose more weight in the long run, so use this metabolic benefit as one factor in choosing your strategy.

Intermittent Energy Restriction (IER) produces short-term weight loss comparable to Continuous Energy Restriction (CER), but offers no significant long-term advantages in anthropometric, cardiometabolic, inflammatory, or appetite outcomes.

If you are considering Intermittent Fasting for weight loss, expect it to work similarly to standard daily calorie restriction in the short term. Do not expect it to provide better long-term health or weight maintenance results than simply counting calories every day. The choice between IER and continuous restriction should be based on which pattern you can stick to consistently, as neither offers a long-term advantage over the other.

Alternate-day modified fasting (ADMF) improves subjective sleep quality (SSQ) and reduces daytime dysfunction compared to daily calorie restriction, but does not significantly change total sleep quality (PSQI) or daytime sleepiness (ESS).

If you are an overweight woman, ADMF may help you feel more rested during the day and improve your subjective sense of sleep quality, even if it doesn't change your total sleep score or daytime sleepiness levels. Focus on the daytime benefits rather than just sleep duration.

Static energy balance models (e.g., the 3500 kcal rule) significantly overestimate weight loss because they ignore adaptive thermogenesis, which causes resting energy expenditure to drop beyond what is explained by the loss of metabolically active tissue.

If you are dieting and hitting a plateau despite strict adherence to a calorie deficit, do not simply slash calories further. Your body has likely triggered adaptive thermogenesis, lowering your metabolic rate to protect fat stores. Recognize this as a biological defense mechanism, not a personal failure. Sustainable weight management may require longer adaptation periods or strategies that preserve fat-free mass, rather than aggressive restriction.

Metabolic adaptation (adaptive thermogenesis) is dynamic and largely reversible; it persists during negative energy balance but diminishes or disappears during weight stability or positive energy balance (refeeding).

Once you stop losing weight and reach your goal weight, your metabolic rate may partially recover if you maintain that weight. However, if you regain weight, the metabolic adaptation may return. Long-term maintenance requires accepting that your maintenance calories may be lower than before your weight loss, due to the loss of metabolically active tissue (FFM).

Intermittent fasting significantly improves lipid profiles by reducing total cholesterol and LDL, but may temporarily increase triglycerides in short-term interventions (≤ 12 weeks).

Intermittent fasting improves total cholesterol and LDL, key markers for heart health. However, be aware that triglycerides may temporarily rise in the first 12 weeks as your body adapts. This is often a transient phase. If you have high baseline triglycerides, consult a healthcare provider and consider longer-term adherence to see the full lipid benefits.

Intermittent fasting significantly reduces diastolic blood pressure but has no significant effect on systolic blood pressure, fasting plasma glucose, or HbA1c in overweight and obese adults.

Intermittent fasting can help lower diastolic blood pressure, a key component of heart health. However, it may not significantly affect systolic blood pressure or blood sugar levels (FPG, HbA1c) in the short term. For comprehensive cardiometabolic health, combine IF with other lifestyle interventions and monitor your specific markers.

Intermittent Energy Restriction (IER) combined with High-Intensity Interval Training (HIIT) produces greater reductions in body weight, body fat percentage, waist circumference, and hip circumference compared to Continuous Energy Restriction (CER) combined with HIIT in overweight/obese adults, although the difference is not statistically significant in a 4-week trial.

If you are overweight or obese, combining High-Intensity Interval Training (HIIT) with an Intermittent Energy Restriction (IER) diet may help you lose more weight and body fat than a standard daily calorie-restricted diet over a short period. Specifically, eating only 30% of your daily calorie needs on two non-consecutive days a week, while eating normally on the other five days, resulted in nearly double the weight loss (4.6 kg vs 2.5 kg) compared to eating 70% of your needs every day. Although the difference wasn't statistically significant in this small 4-week study, the trend favors IER for body composition improvements.