“Eliminating carbohydrates from the diet causes fat loss regardless of total caloric intake.”

Paoli et al. focused on natural bodybuilders over 8 weeks with equal total energy and protein intake conditions: one group followed the KD, whereas the other adhered to a conventional diet. The results indicated that the KD group significantly reduced body fat more than the conventional diet group.

In the present meta-analysis of randomized controlled trials comparing low-carbohydrate diets with low-fat diets, we found that both diets were equally effective at reducing body weight and waist circumference. Reductions in body weight, waist circumference and other metabolic risk factors were not significantly different between the 2 diets. These findings suggest that low-carbohydrate diets are at least as effective as low-fat diets at reducing weight and improving metabolic risk factors.

When on the low-fat diet, the participants ate 550 to 700 fewer calories per day than when on the low-carb diet. Despite the large differences in calorie intake, they reported no differences in hunger, enjoyment of meals, or fullness between the two diets. People lost weight on both diets, but only the low-fat diet led to a significant loss of body fat.

We selectively restricted dietary carbohydrate versus fat for 6 days following a 5-day baseline diet in 19 adults with obesity confined to a metabolic ward where they exercised daily. Subjects received both isocaloric diets in random order during each of two inpatient stays. Whereas carbohydrate restriction led to sustained increases in fat oxidation and loss of 53 ± 6 g/day of body fat, fat oxidation was unchanged by fat restriction, leading to 89 ± 6 g/day of fat loss, and was significantly greater than carbohydrate restriction (p = 0.002).

Dietary carbohydrate restriction has been purported to cause endocrine adaptations that promote body fat loss more than dietary fat restriction. We selectively restricted dietary carbohydrate versus fat for 6 days following a 5 day baseline diet in 19 adults with obesity confined to a metabolic ward where they exercised daily. Remarkably, fat oxidation on the reduced fat diet remained unchanged and resulted in a greater rate of body fat loss compared to the reduced carbohydrate diet, despite being equivalent in calories.

The isocaloric KD was not accompanied by increased body fat loss but was associated with relatively small increases in EE that were near the limits of detection with the use of state-of-the-art technology. Subjects lost weight and body fat throughout the study corresponding to an overall negative energy balance of ∼300 kcal/d. Compared with BD, the KD coincided with increased EEchamber (57 ± 13 kcal/d, P = 0.0004) and SEE (89 ± 14 kcal/d, P < 0.0001) and decreased RQ (−0.111 ± 0.003, P < 0.0001).

In a randomized controlled trial conducted in 36 patients with metabolic syndrome demonstrated that even without instructions to reduce calories, participants on a very-low carbohydrate diet or a low-fat diet reduced caloric intake and lost weight, with those enrolled in the very-low carbohydrate diet group experiencing significantly more weight loss than those enrolled in the low-fat diet group after 12 weeks. The very-low carbohydrate diet also resulted in more significant improvements in abdominal fat and serum triglycerides.

Results from two well-controlled metabolic ward studies also support this conclusion, in terms of the substitution of fat in place of carbohydrates resulting in higher EE. One study involved comparing 17 men with overweight or obesity consuming either an isocaloric high-carbohydrate diet (50% CHO, 15% protein, 35% fat) or a very-low-carbohydrate diet (5% CHO, 15% protein, 80% fat) for 4 weeks to assess changes in EE and body composition. The EE was 153 kcal/d higher during the low-carbohydrate phase.

The reduction of carbohydrate intake without restricting caloric intake is more potent to achieve weight loss over 12 weeks when compared to a calorie-restricted diet in overweight/obese adults. The combination of restricting carbohydrate and total calorie intake may augment the beneficial effects of reducing BMI, body weight, and metabolic risk factors among overweight/obese individuals.

Carbohydrate-restricted diets can reduce body weight by reducing appetite via the production of ketone bodies, increasing energy expenditure and insulin sensitivity, and stimulating lipolysis. Our dose–response meta-analyses indicated a proportional reduction in body weight with the decrease in carbohydrate intake, with the greatest reduction in body weight at 5–10% carbohydrate intake, suggesting that very-low-carbohydrate (ketogenic) diets are the most effective diets among different types of carbohydrate-restricted diets for weight loss.

A meta-analysis of 13 randomized controlled trials... found that the ketogenic diet produced a small but significantly greater reduction in weight... compared with the low-fat diet at one year. The ketogenic diet provided about 980 calories... while the Mediterranean diet provided about 1800 calories.

LCD may promote fat mass loss and regulation of biochemical parameters, such as lipid and glycemic biomarkers. Reduction of CHO intake decreases muscle glycogen, yielding greater fat oxidation and associated metabolic benefits.

Systematic reviews with pairwise and network meta-analyses of the best available evidence have failed to show the superiority of low-carbohydrate diets on long-term clinical weight loss outcomes or that all sources of carbohydrate behave equally.

Several logical consequences of this carbohydrate-insulin model of obesity were recently investigated in a pair of carefully controlled inpatient feeding studies whose results failed to support key model predictions. Therefore, important aspects of carbohydrate-insulin model have been experimentally falsified suggesting that the model is too simplistic.

Low carbohydrate diets, including high-fat, 'ketogenic' diets, have moved to the forefront of popular diets promoted for weight loss... Outcome Measure: Body weight... Body fat via dual energy x-ray absorptiometry (DXA)... 6 months.

Neither option is superior: Cutting either carbs or fats shaves off excess weight in about the same proportion, according to the study. What's more, the study inquired whether insulin levels or a specific genotype pattern could predict an individual's success on either diet. The answer, in both cases, was no.

Low-carb diets, especially very low-carb diets, may lead to greater short-term weight loss than low-fat diets. But most studies have found that at 12 or 24 months, the benefits of a low-carb diet aren't very large or can't be kept up. Cutting calories and carbs may not be the only reason low-carb diets can lead to weight loss.

Eighty three subjects... were randomly allocated to one of 3 isocaloric weight loss diets (6 MJ) for 8 weeks... Percent fat mass loss was not different between diets VLCARB -4.5 ± 0.5, VLF-4.0 ± 0.5, HUF -4.4 ± 0.6 kg). Isocaloric VLCARB results in similar fat loss than diets low in saturated fat, but are more effective in improving triacylglycerols, HDL-C, fasting and post prandial glucose and insulin concentrations.

People who followed a low-carbohydrate, high-protein diet lost more weight than people on a low-fat, low-cholesterol, low-calorie diet during a six-month comparison study at Duke University Medical Center. Along with losing an average of 26 pounds, dieters assigned to the low-carbohydrate plan lost more body fat... The low-fat, low-cholesterol, low-calorie group followed a diet consisting of less than 30 percent of daily caloric intake from fat... and were also advised to cut back on calories. The recommended daily calorie level was 500 to 1,000 calories less than the participant's maintenance diet.

For these people, a diet much lower in carbohydrates — around 25% of calories — can be a more effective way to lose weight and improve the metabolic syndrome than a low-fat diet. But the study doesn't prove that low-carb diets work better than low-fat diets for everyone.

A year-long randomized clinical trial (DIETFITS) has found that a low-fat diet and a low-carb diet produced similar weight loss and improvements in metabolic health markers. Furthermore, insulin production and tested genes had no impact on predicting weight loss success or failure. Thus, evidence to date indicates you should choose your diet based on personal preferences, health goals, and sustainability. ... No significant weight-loss differences were seen between the low-fat and low-carb groups, and neither genetics nor insulin production could predict weight-loss success on either diet.

Isocaloric VLCARB results in similar fat loss than diets low in saturated fat, but are more effective in improving triacylglycerols, HDL-C, fasting and post prandial glucose and insulin concentrations. ... As previously shown, the amount of fat loss was similar on all diets when the same energy restriction is applied.

The energy intake between LCHF and HCLF treatments remained isocaloric. ... There were no significant treatment or interaction effects for weight or body composition during either LCHF or HCLF (Table 3). Overall changes in weight and body composition on each diet were similar.

When mice continue to eat the high-fat, low-carb diet beyond one week... they consume more fat than they can burn, and develop diabetes and obesity. Long-term clinical studies in humans are still necessary.

It is increasingly clear that the idea that "a calorie is a calorie" is misleading. The calorie content may not be as predictive of fat loss as is reduced carbohydrate consumption. ... Greene et al. found that people eating an extra 300 kcal a day on a very-low-carbohydrate diet lost a similar amount of weight during a 12-week study as those on a low-fat diet [19]. Over the course of the study, subjects consumed an extra 25,000 kcal that should have added up to about a 7 pounds weight gain; it did not.

A calorie deficit drives weight loss by forcing the body to use stored fat for energy, while a low-carb diet reduces carbohydrate intake to shift metabolism towards fat oxidation; the two approaches frequently overlap in practice. A calorie deficit occurs when you consume fewer calories than your body expends over a given period.

It's true that Dr. Atkins and many low-carb experts told us not to worry about counting calories in the beginning—but that doesn't mean that calories don't count. Because they do. If you eat too much of anything (even food low in carbs), you will not lose weight.

Scientific consensus in nutrition holds that fat loss requires a sustained caloric deficit, regardless of macronutrient composition. Low-carb diets like keto often lead to spontaneous calorie reduction via appetite suppression, but isocaloric trials show no superior fat loss compared to other diets.

A calorie deficit diet centers on consuming fewer calories than your body burns, fostering weight loss regardless of food types. In contrast, the ketogenic diet emphasizes a high-fat, low-carb, and moderate-protein approach, shifting the body into ketosis—a state where fat becomes the primary energy source. Keto often leads to quicker initial weight loss due to reduced insulin and appetite suppression, though maintaining ketosis requires strict adherence.