In the ongoing debate over the best way to lose weight and restore metabolic health, the ketogenic diet continues to spark controversy and curiosity in equal measure. A recent 2025 review in the peer-reviewed journal Nutrients takes a methodical look at the data—and what it finds is striking.
The review examines 12 randomized controlled trials (RCTs) published over the past decade, all comparing ketogenic diets (KDs) to other dietary strategies. The results? In nearly every case, the ketogenic group lost more weight, improved blood sugar markers more significantly, and often achieved these results without restricting calories.
But before jumping to conclusions, it’s important to understand what the data actually shows—and just as importantly, what it doesn’t.
Ketogenic Diets vs. Conventional Diets
The trials reviewed compare ketogenic diets to a wide range of alternatives: low-fat diets, calorie-restricted diets, and standard nutrition guidelines from organizations like the American Diabetes Association. Many of the studies were carefully matched for total calories, or allowed participants in both groups to eat freely (ad libitum), removing caloric intake as a confounding variable.
One of the standout findings comes from a study where participants on a ketogenic diet lost an average of 12.7 kg (28 lbs) over 32 weeks—more than four times the weight lost by those on the control diet, which followed ADA guidelines. The ketogenic group also saw greater reductions in HbA1c (a long-term marker of blood sugar) and triglycerides. Notably, only 8% of the ketogenic group dropped out, compared to 46% in the control group.
Another RCT found that when participants followed a very-low-carbohydrate ketogenic diet versus a moderate-carb, low-fat diet—both with equal calories—the ketogenic group still lost more weight. In fact, even though both groups consumed roughly the same amount of calories, the keto group saw significantly more fat loss and a greater drop in HbA1c over 12 months.
Appetite Control Without Calorie Counting
Across many of the trials, a recurring pattern emerged: people on ketogenic diets tended to naturally eat less, even when they weren’t told to restrict their intake. This suggests that the satiety effect of high-fat, low-carb eating may help regulate hunger in ways that conventional calorie restriction cannot.
In one trial, participants who followed a ketogenic diet ad libitum (eating as much as they wanted) lost significantly more weight than a group following a strict calorie-restricted plan. The researchers speculated that this “natural calorie reduction” was a result of the diet’s appetite-suppressing effects—likely driven by stabilized blood sugar and hormonal responses.
Not Just for Obesity—Athletic Populations Benefit Too
Interestingly, the review doesn’t just focus on overweight individuals. Several studies involved athletes, including weightlifters and semi-professional footballers. In one crossover trial with competitive lifters, participants lost an average of 3.3 kg more body weight during the ketogenic diet phase compared to their normal diet phase, with no loss of strength or performance.
In another study, footballers on a ketogenic diet saw a greater reduction in body fat, waist circumference, and visceral fat than their peers following a Western diet, all in just four weeks.
Improvements Beyond the Scale
Several RCTs also recorded improvements in metabolic markers. Fasting insulin levels dropped more steeply in the ketogenic groups, insulin sensitivity improved, and liver enzyme levels normalized. One study found that 44% of participants on a ketogenic diet were able to discontinue at least one diabetes medication—compared to just 11% in the control group.
Resting metabolic rate (RMR), often a casualty of weight loss, was better preserved in keto groups. In one trial, the ketogenic group had a smaller drop in RMR than those following a standard low-calorie diet—suggesting less metabolic slowdown during weight loss.
A Note On Carnivore
While the RCTs in this review were conducted on ketogenic diets that included low-carb vegetables and some plant-based foods, the authors of the Nutrients article also discuss emerging interest in stricter approaches—specifically, very low to zero-carbohydrate diets, often referred to as carnivore.
Though formal clinical trials on carnivore are still limited, its structure—animal-based, ultra-low-carb, free from seed oils and processed additives—is metabolically aligned with the ketogenic protocols shown to be effective in the reviewed RCTs. The theoretical mechanisms are the same: insulin regulation, appetite normalization, nutrient density, and elimination of inflammatory inputs.
In that light, carnivore can reasonably be viewed as a more targeted extension of the ketogenic approach. While researchers have yet to run full-scale RCTs on carnivore itself, its overlap with successful ketogenic strategies—and the growing body of real-world results—suggest it may offer similar or even enhanced benefits for certain individuals.
The Bottom Line
The science is increasingly clear: in controlled settings, ketogenic diets consistently outperform conventional low-fat or calorie-restricted diets—not just in weight loss, but in metabolic health, hunger control, and adherence.
For individuals with obesity, insulin resistance, or type 2 diabetes, a well-formulated ketogenic diet offers a powerful alternative backed by hard data. But as with all dietary strategies, more research is needed, especially for variations like carnivore that have yet to undergo rigorous testing.
Still, if the results of these trials are any indication, low-carb eating isn’t just a fad. It’s a legitimate clinical tool—and one that’s earning its place in the modern medical toolkit.
Dave Soulia | FYIVT
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