Low-Carb vs. Low-Fat Diet: Which One is Better for Weight Loss?

If you're trying to lose weight, you've probably heard about two main approaches: cutting carbs or cutting fats. But which one actually works better?

In recent years, these two strategies have been at the center of debate. Low-carb diets (LC) have gained popularity for their ability to trigger rapid weight loss , w(1)hile low-fat diets (LF) continue to be recommended based on the idea that reducing fat intake prevents fat accumulation in the body (2).

But is one really better than the other? In this article, we break down what science says.

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What is a Low-Carb Diet?

A low-carb diet limits carbohydrate intake to less than 26% of total daily calories (up to 130g/day), with stricter versions reducing intake to less than 10% (20-50g/day) (3).

For reference, in a standard diet, carbohydrates make up 45-65% of total daily calories, which is around 225-325g per day. In a low-carb diet, intake drops to 20-130g per day.

One of the most noticeable effects of this type of diet is rapid weight loss in the first few days. However, this does not necessarily mean fat loss.

The body stores carbohydrates as glycogen, primarily in the liver and muscles. Each gram of glycogen binds to approximately 3 grams of water, meaning its storage also involves water retention.

When carb intake is drastically reduced, the body starts using its glycogen stores for energy. As glycogen is depleted, the water associated with it is also lost, leading to a quick drop on the scale—but without significant fat loss.

If carb intake remains low for an extended period, such as in a ketogenic diet, the body stops relying on carbohydrates as its primary fuel source and shifts to using more fat for energy. With fewer carbohydrates available, the body continues depleting glycogen, and once those stores are gone, it turns to fat as fuel.

Part of this fat is converted into ketone bodies, an alternative energy source that the brain and other organs can use.

However, it’s important to note that the initial weight loss in this type of diet is mostly due to water loss along with glycogen, rather than immediate fat burning.

👉 The scale doesn’t tell the whole story. Your weight includes fat, muscle, water, and food in transit.

What is a Low-Fat Diet?

Unlike low-carb diets, low-fat diets (LFD) focus on reducing fat intake to less than 30% of total daily calories, typically ranging between 11% and 19% (4,5).

Why Are Low-Fat Diets Popular for Weight Loss?

Low-fat diets are often recommended because they help reduce total calorie intake.

The reasoning behind this is that fat is more calorie-dense than other macronutrients:

• Fat: 9 kcal per gram
• Protein & Carbohydrates: 4 kcal per gram

For example:

• 100g of oil (pure fat) contains 884 kcal.
• 100g of sugar (pure carbohydrates) contains 384 kcal, less than half the calories.

This has led to the belief that fat promotes weight gain, and that by reducing fat intake, losing weight becomes easier (4,6).

But is it really necessary to avoid fats?

While reducing fat can be an effective strategy to lower calorie intake, it doesn’t mean you should eliminate fats completely or fear them. Fats play essential roles in hormone production and the absorption of fat-soluble vitamins.

That being said, lowering fat intake can help with weight loss—as long as it doesn’t lead to an increase in calorie consumption from other macronutrients. However, it’s not the only way to create a calorie deficit, and it certainly doesn’t mean you should eliminate fats entirely.

So... Which Diet is Better for Weight Loss?

This is one of the most common questions in the world of dieting, but the answer is clear: Neither diet is inherently better than the other.

Weight loss ultimately depends on maintaining a calorie deficit and being able to stick to a plan long-term, rather than which macronutrient you cut.

Both low-carb and low-fat diets can be effective, as long as they align with your preferences and lifestyle.

What Does the Science Say?

📌The DIET FITS study followed 609 people with obesity for 12 months, comparing a low-fat diet and a low-carb diet. Both groups lost an average of 5-6 kg, with no significant differences between them (7).

These findings are consistent with a meta-analysis of 739 participants, which found only a slight advantage of 1.01 kg for low-carb diets, but with no clinically significant impact (8).

So, What Really Matters?

What truly determines a diet’s success is not whether it’s low in carbs or fats, but rather:

✔ That you can maintain a calorie deficit.
✔ That the diet is sustainable for you in the long run.

Both approaches can work, but the best diet for you is the one that fits your preferences, lifestyle, and needs. The most important thing is finding a method you can follow consistently without feeling restricted or sacrificing your well-being.

Conclusion

If you were expecting a definitive answer, the truth is both strategies can work. Low-carb and low-fat diets are both effective, as long as they help you maintain a calorie deficit and are sustainable long-term.

It’s not just about what you cut out—it’s about what you can maintain over time. Find the method that works best for you and prioritize food quality.

There is no single “best” diet for weight loss. What truly matters is maintaining a calorie deficit in a sustainable way while choosing nutritious foods.

👉 With Fitia, you can calculate your calorie and macro needs to find the approach that works best for you. Download it for free here.