Browse the evidence

Weight loss via calorie restriction alone, without resistance training, leads to a loss of appendicular lean mass and an increased prevalence of sarcopenia in breast cancer survivors.

If you lose weight through diet alone, you risk losing muscle mass, which can lead to sarcopenia. To preserve muscle, combine calorie restriction with resistance training.

Intermittent energy restriction (IER) using a 'week-on, week-off' strategy produces weight loss and weight loss maintenance comparable to continuous energy restriction (CER) over 12 months.

If you find daily calorie counting unsustainable, try a 'week-on, week-off' approach. Eat your normal diet for one week, then restrict calories (e.g., to ~1300 kcal) for the next week. Repeat this cycle for a year. This study shows you can achieve the same weight loss and maintenance as eating restricted calories every day, which may help you stick with it longer.

Short-term weekly intermittent energy restriction (IER) produces weight loss equivalent to continuous energy restriction (CER) in adults with overweight or obesity, making it a viable alternative treatment option.

If you struggle with daily calorie counting, try a weekly intermittent energy restriction plan where you restrict calories (420-1500 kcal) for 2-3 days a week (or in 7-day cycles) and eat normally otherwise. This approach yields the same weight loss as daily restriction over 3-6 months. However, be aware that long-term maintenance is not guaranteed by the diet alone; you likely need active weight maintenance strategies after the intervention ends.

While IER+MED reduces visceral adipose tissue (VAT) more than DASH, this advantage disappears when adjusting for total fat mass loss, suggesting the VAT reduction is proportional to overall weight loss rather than specific to visceral fat mobilization.

Don't expect intermittent fasting to melt belly fat faster than other diets if you lose the same amount of total weight. The VAT reduction you see is largely due to overall fat loss. Focus on the total fat loss and the sustainability of the diet pattern.

Resistance training alone significantly increases lean mass in overweight/obese premenopausal women, even without a prescribed caloric deficit.

If your goal is to build muscle or improve your shape without losing weight, resistance training is effective even if you don't change your diet. Focus on progressive overload with compound exercises. However, be aware that without a caloric deficit, you will not lose fat, so your weight might stay the same or increase slightly due to muscle gain.

Intermittent energy restriction (IER) reduces body weight and fat mass compared to a usual diet, with effects on weight loss being similar to continuous energy restriction (CER).

If you struggle with daily calorie counting, try Intermittent Energy Restriction (IER). This involves restricting calories to 20-25% of your normal intake (or fasting completely) on 1-2 days per week (like the 5:2 diet) or every other day (ADF), while eating normally on other days. This approach reduces body weight and fat mass just as effectively as continuous daily restriction, offering more flexibility.

Significant weight loss (approx. 24%) achieved via a very low calorie diet (550 kcal/day) significantly improves circulating levels of adiponectin and leptin, whereas a low carbohydrate/high protein diet yielding minimal weight loss does not.

To improve your adiponectin and leptin levels, focus on achieving significant weight loss. This study shows that a very low-calorie diet (around 550 kcal/day) combined with behavioral support led to substantial weight loss (~24%) and significant improvements in these hormones. A low-carb diet that does not result in weight loss did not produce these benefits, suggesting that the weight loss itself is the primary driver of metabolic improvement, not the specific macronutrient ratio.

Fat loss magnitude is determined exclusively by the size of the energy deficit, regardless of whether that deficit is created through dietary restriction alone or a combination of diet and aerobic exercise.

To lose fat, you must create a caloric deficit. Whether you achieve this deficit by eating less, moving more, or a combination of both, the amount of fat you lose will be determined by the size of that deficit, not the method used. If you match the deficit, diet-only and diet-plus-exercise yield equivalent fat loss, though exercise improves fitness.

A high-protein diet during energy restriction activates mitochondrial oxidation, which is positively correlated with resting energy expenditure and inversely related to fat mass, potentially explaining the enhanced weight loss.

High-protein diets may work by boosting your mitochondria's ability to burn fuel, which helps maintain your metabolic rate and burn more fat, even when you are eating fewer calories.

The reduction in energy intake from lower energy density meals is linearly related to the change in energy density, with stronger effects in adults than children and in entrée designs compared to preloads.

The calorie-reducing effect of low energy density foods is strongest in adults and when consumed as main meals (entrées). In children, the effect is smaller, and preloads may be less effective than main meals.

Adherent caloric restriction in overweight/obese women induces metabolic adaptation, evidenced by a significant decrease in Resting Energy Expenditure (REE) that exceeds the reduction predicted by changes in Fat-Free Mass (FFM).

If you are losing weight through calorie restriction, expect your resting metabolism to drop significantly (approx 10% in this study) beyond what you would predict just from losing weight. This is a biological defense mechanism, not a failure. To maintain weight loss, you must account for this lower energy expenditure, likely by adjusting your caloric intake or increasing physical activity to offset the metabolic slowdown.

Intermittent energy restriction (IER) produces superior short-term weight loss and fat mass reduction compared to continuous energy restriction (CER) in primary care settings, but is associated with higher attrition and rapid weight regain after intervention cessation.

If you try Intermittent Energy Restriction (eating very little on 2 days, normal on 5), you might lose weight faster in the first 6 months than if you cut calories every day. However, be aware that this approach is harder to stick with long-term; many people quit or regain the weight once they stop the strict fasting days. It works best if you have medical support to manage side effects like dizziness.

Intermittent energy restriction (IER) leads to greater reductions in systolic blood pressure and fat mass compared to continuous energy restriction (CER) in the short term, but these benefits are transient and revert to baseline after the intervention ends.

IER can improve blood pressure and reduce fat mass more effectively than daily calorie restriction in the short term. However, these health benefits disappear if you stop the diet, so maintaining the lifestyle change is critical for sustained cardiovascular health.

A ketogenic diet promotes rapid fat mass loss in obese individuals, primarily through caloric restriction and appetite suppression rather than a unique metabolic advantage.

If you are obese, a ketogenic diet can help you lose fat quickly, but this is largely because it helps you eat fewer calories by suppressing appetite (lowering ghrelin). It is not magically better than other diets if you eat the same number of calories. Focus on the caloric deficit and the ease of appetite control.

A Low-Energy Diet (LED) of 850 kcal/day produces statistically equivalent weight loss and long-term maintenance compared to a Very-Low-Energy Diet (VLED) of 520 kcal/day, while offering a safer profile with fewer adverse events and reduced need for medical monitoring.

You do not need to eat fewer than 800 calories a day to lose weight effectively. A structured 850-calorie liquid diet program produces the same amount of weight loss and long-term maintenance as a more extreme 520-calorie diet, but with fewer side effects like fatigue and hair loss. Focus on a sustainable plan that includes behavioral support rather than trying to minimize calories as low as possible.

A 6-week Mediterranean diet combined with 5 days of semi-fasting (600-700 kcal) produces weight loss and body composition improvements equivalent to a standard hypocaloric Mediterranean diet without fasting.

You can lose weight effectively by simply reducing your daily calories by 500 kcal while following a Mediterranean diet pattern. Adding a 5-day semi-fast period (consuming 600-700 kcal of liquid/pureed meals) does not provide a significant advantage in weight loss over the standard diet alone. If you choose to try the semi-fast, be aware that it requires significant preparation and may not be sustainable for everyone long-term.

Intermittent fasting (IF) produces a statistically significant greater reduction in Body Mass Index (BMI) compared to continuous energy restriction (ER), although the absolute difference in total body weight loss is not statistically significant.

If you are trying to lose weight, intermittent fasting may help you reduce your BMI slightly more than just counting calories every day, even if the scale doesn't move much faster. Try a 16:8 schedule (fast for 16 hours, eat within 8 hours) or alternate-day fasting. Be aware that you might feel dizzy, while those just cutting calories might get more headaches. The key is consistency with whichever method you choose.

Intermittent fasting and continuous energy restriction produce similar improvements in blood pressure (systolic and diastolic), LDL cholesterol, and HDL cholesterol, with no statistically significant differences between the two methods.

If your goal is to lower blood pressure or improve cholesterol, you do not need to fast. Reducing your overall calorie intake through standard dieting is just as effective as intermittent fasting for these specific heart health markers. Focus on the total amount of food you eat rather than when you eat it for these outcomes.

Intermittent fasting and continuous energy restriction produce similar improvements in fasting plasma glucose levels, with no statistically significant difference between the two methods.

If your goal is to improve blood sugar levels, you do not need to fast. Reducing your overall calorie intake through standard dieting is just as effective as intermittent fasting for glycemic control. Focus on the total amount of food you eat rather than when you eat it for these outcomes.

Long-term high-intensity interval training (HIIT) using leg ergometry causes significant regional fat loss in the thighs and visceral adipose tissue, but does not significantly reduce total body fat mass or trunk fat.

If you want to lose fat specifically from your thighs and belly without necessarily dropping total body weight, try 16 weeks of HIIT using a leg bike. Do 8-12 sets of 1-minute sprints at >90% effort, twice a week, with 1-minute recovery. Expect your thigh fat to decrease, but don't be surprised if the scale stays the same because you might be building muscle.

A 7-day diet-induced energy restriction of 50% TDEE reduces body mass and fasting blood glucose without eliciting compensatory decreases in basal metabolic rate (BMR) or physical activity energy expenditure (PAEE) in overweight and obese adults.

If you are overweight or obese, a strict 7-day liquid diet cutting your calories in half can produce initial weight loss and improve blood pressure and glucose without causing your body to immediately slow down its metabolism or reduce your spontaneous movement. This suggests short-term aggressive restriction can be a viable strategy for initial health improvements, though long-term maintenance requires different strategies.

A 12-week very low-calorie ketogenic diet (800-1000 kcal/day, 70% fat, 20% protein, 10% carbs) significantly reduces body weight and body fat percentage in overweight/obese adults, but also significantly decreases resting metabolic rate (RMR) and total energy expenditure.

A 12-week very low-calorie ketogenic diet (800-1000 calories, high fat) leads to significant fat loss in obese individuals, but it also significantly slows down your resting metabolism. This metabolic slowdown is a normal adaptive response to severe calorie restriction and should be expected. Long-term maintenance requires careful refeeding strategies to mitigate metabolic adaptation.

Intermittent energy restriction (IER) produces weight loss comparable to continuous energy restriction (CER) in overweight and obese adults over short-term periods (up to 12 months).

If you are overweight or obese, intermittent fasting (eating very little on 1-6 days a week) will help you lose weight just as well as eating a little less every day. It is not a magic bullet for superior weight loss, but it is a valid alternative strategy. Choose the pattern that you can stick to for at least 12 weeks.

Intermittent Caloric Restriction (ICR) helps overcome metabolic adaptation (slowed resting metabolic rate) associated with continuous caloric restriction.

If you feel your metabolism slowing down on a strict diet, try an intermittent approach (like ICR) which might help overcome metabolic adaptation.