Is it better to cut carbs or fat when cutting for fat loss?

October 22, 2025 •

3 min read

Recent research from the National Institutes of Health showed that, under controlled conditions, cutting fat led to greater body fat loss than cutting carbohydrates, but experts emphasize sustainability is key. The question of whether it is better to cut carbs or fat when cutting is highly debated in the fitness world, with evidence suggesting that the best approach depends on individual factors, metabolic response, and personal preference.

Quick Summary

An analysis of low-carb vs. low-fat cutting strategies reveals both can be effective for fat loss within a calorie deficit. The optimal choice depends on metabolic response, exercise type, and long-term adherence. Both diets affect fat loss, muscle preservation, and hormone levels differently, making a personalized approach most effective.

Key Points

Calorie Deficit is Paramount: True fat loss only occurs when you consume fewer calories than you burn, regardless of your macronutrient split.
High Protein is Key: A high protein intake is essential for preserving muscle mass and promoting satiety during a cut, making the process more manageable.
Low-Carb Offers Quick Water Loss: Initial weight loss on a low-carb diet is often faster due to the depletion of glycogen and associated water weight, but this isn't true fat loss.
Low-Fat Aids Calorie Restriction: Given fat's high caloric density, a low-fat diet can make it easier to achieve a calorie deficit by replacing high-calorie fat sources with lower-calorie, high-volume foods.
Consider Your Activity Level: Athletes engaging in high-intensity training often need adequate carbohydrates to fuel performance and prevent fatigue, making severe carb restriction counterproductive.
Sustainability Over Extremism: The most effective diet is the one you can stick to consistently. An overly restrictive approach, whether low-carb or low-fat, can lead to cravings and burnout.
Personalize Your Macros: Start with a balanced ratio and adjust based on your energy levels, hunger, and workout performance. Monitor how your body responds and modify your approach accordingly.

The Fundamental Role of a Calorie Deficit

Regardless of whether you choose to restrict carbohydrates or fat, the fundamental principle of fat loss remains a calorie deficit. This means consistently consuming fewer calories than your body expends. Manipulating the macronutrient ratios is a tool to make this deficit more manageable and to optimize body composition, but it does not supersede the importance of overall energy balance. Studies have repeatedly shown that when calories are matched, the long-term difference in weight loss between low-carb and low-fat diets is often minimal. The primary benefit of a specific macronutrient approach lies in its impact on satiety, energy levels, and adherence.

The Case for Cutting Carbohydrates

One of the most popular strategies for fat loss involves reducing carbohydrate intake. This approach can influence metabolism to aid in fat loss.

How Low-Carb Diets Work

Low-carb diets, which are typically higher in protein and fat, can increase satiety and reduce appetite, making a calorie deficit easier to manage. Reducing carbohydrates also lowers blood glucose and insulin levels. Lower insulin levels may facilitate greater fat mobilization and burning. Initially, low-carb diets can lead to rapid water weight loss as glycogen stores are depleted.

Potential Downsides of Cutting Carbs

For athletes, severely restricting carbohydrates can impair performance, especially in high-intensity activities that rely on glycogen for fuel. The transition to low-carb may also cause initial side effects like headaches and fatigue. While adequate protein and resistance training are key for muscle preservation on any diet, carbohydrates are considered 'protein sparing,' potentially helping to prevent muscle breakdown.

The Argument for Cutting Fat

Reducing fat intake is another effective cutting strategy.

How Low-Fat Diets Work

Since fat has more than double the calories per gram compared to carbs and protein, reducing fat is an efficient way to lower calorie intake. Replacing high-fat foods with high-volume, low-fat options can promote fullness on fewer calories. Some controlled studies suggest a low-fat diet may lead to greater overall fat loss than a calorically matched low-carb diet. Low-fat diets focusing on whole foods can also ensure a high intake of vitamins and fiber.

Potential Downsides of Cutting Fat

Severely restricting fat (below 20% of calories) can negatively impact hormone production, including testosterone, which is important during calorie restriction. Compared to fat and protein, carbohydrates are digested more quickly, potentially leading to less sustained fullness on a low-fat, high-carb diet. A very low-fat diet can also be less palatable, potentially hindering adherence.

Comparison Table: Low-Carb vs. Low-Fat for Cutting


Feature	Low-Carb Approach	Low-Fat Approach
Satiety	High, primarily from protein and fats.	Can be lower, especially if fiber is lacking.
Initial Weight Loss	Rapid, due to water loss from glycogen depletion.	Steady, without the initial water weight fluctuation.
Exercise Performance	Can be impaired, especially for high-intensity training.	Fuels high-intensity performance effectively with sufficient carbs.
Muscle Preservation	Requires adequate protein and resistance training.	Carbs are 'protein sparing', helping preserve muscle.
Adherence	Depends heavily on individual preference and tolerance for carb restriction.	Can be challenging due to bland food and potential hunger, but can be highly sustainable with proper food choices.
Hormonal Health	Risk to testosterone if fats are too low, but overall balanced if macros are moderate.	Risk to hormones if fat is too severely restricted.

How to Find Your Best Approach

The most effective cutting strategy is one you can maintain consistently. A balanced approach often works best. Follow these steps:

Calculate Your Calorie Target: Determine your calorie needs and create a moderate deficit (20-25%).
Prioritize Protein: Aim for 1.6–2.2 g/kg body weight of protein to preserve muscle and increase satiety.
Experiment and Adjust: Start with a moderate macro split (e.g., 40% carbs, 30% protein, 30% fat) and see how you feel. Adjust based on energy, hunger, and performance.
Emphasize Food Quality: Focus on whole, nutrient-dense foods like complex carbs, healthy fats, and lean proteins.
Listen to Your Body: Pay attention to how your body responds and adjust your diet for sustainability and well-being.

Conclusion

The most effective strategy for cutting involves a sustainable calorie deficit that aligns with individual needs and preferences, rather than strictly cutting carbs or fat. While low-carb can offer quicker initial results due to water loss, low-fat might lead to more controlled fat loss in some cases. Athletes may benefit from maintaining carbohydrate intake for performance. Prioritizing protein, maintaining a moderate deficit, and finding a balanced macro approach that supports long-term adherence are key to successful fat loss. More information on effective cutting strategies.

Frequently Asked Questions

For short-term weight loss, a low-carbohydrate diet can often yield faster initial results due to significant water weight loss from depleted glycogen stores. However, this rapid weight change is not indicative of long-term fat loss success.

The best choice depends on your individual metabolism, preferences, and lifestyle. For high-intensity athletes, maintaining carbohydrate intake is often necessary for performance. For others, personal preference and adherence are the most important factors for long-term success.

Yes, severely restricting fat intake (below 20% of total calories) can negatively impact hormone production, including testosterone, which can affect overall health and muscle preservation.

Research suggests that as long as protein intake is sufficient and resistance training is performed, both low-carb and higher-carb diets can preserve muscle mass effectively during a cut. Adequate carbs can be 'protein sparing,' preventing muscle from being used for energy.

You can lose muscle if you don't consume enough calories and protein, and not necessarily just from cutting carbs. If protein intake is adequate and you continue resistance training, muscle can be preserved. However, severe carb restriction can lead to fatigue that hinders high-intensity workouts necessary for muscle preservation.

Protein is arguably the most critical macronutrient when cutting. A high protein intake (1.6-2.2 g/kg body weight) helps maximize satiety and preserves lean muscle mass in a calorie deficit, ensuring you lose fat, not muscle.

A solid starting point is often a balanced approach, such as 40% carbs, 30% protein, and 30% fat. This provides a good balance for energy, satiety, and muscle preservation, which can then be adjusted based on individual response.