If you’ve ever found yourself stuck between trying a low-carb or low-fat diet, you’re not alone.
Both are popular for fat loss, but are the results really that different? Let’s break down what the science actually says.

What the Research Shows

A large meta-analysis by Hall & Guo (2018) compared 32 controlled feeding studies, meaning participants’ diets were precisely managed and calorie-matched between groups.

• One group followed a lower-fat, higher-carb approach.

• The other followed a lower-carb, higher-fat approach.

Results?
Both groups had similar metabolic rates and similar rates of fat loss.
Interestingly, the lower-fat group showed a tiny edge, burning about +26 kcal/day more and losing ~16 g/day more fat than the low-carb group, but the difference was practically insignificant.

Takeaway: When calories and protein are equal, it doesn’t matter whether your remaining calories come from carbs or fats.

A More Recent Study (Hall et al., 2021)

In a more controlled trial, researchers compared two extreme diets over two weeks:

• Keto (very low carb): 75% fat, 15% protein, 10% carbs

• Low-fat vegan: 75% carbs, 15% protein, 10% fat

Participants could eat as much or as little as they wanted, as long as they stuck to their macronutrient ratios.

What Happened

• Those on the low-fat vegan diet naturally ate ~689 kcal/day less than the keto group.

• The keto group lost 1.8 kg, but 1.6 kg of that was water, not fat.

• The low-fat group lost about 1 kg of actual fat, purely due to their lower calorie intake.

This shows that while keto may cause rapid weight loss, most of it comes from water, not body fat.

So, What Does This Tell Us?

This study wasn’t designed to crown a “winner” for fat loss; rather, it compared how two extremes affect appetite and metabolism.
The findings highlight that:

• You don’t need to cut carbs to lose fat.

• Keto isn’t necessarily superior for appetite suppression or satiety.

• Whether you go low-carb or low-fat, the total calorie and protein intake matter most.

Practical Takeaways

1. Choose the approach that fits your lifestyle.
   Love carbs? Keep them. Prefer fattier foods? That’s fine too.
   As long as calories and protein are right, you can lose fat either way.

2. Focus on food quality.
   Aim for 80% whole, nutrient-rich foods: fruit, veg, lean proteins, whole grains, nuts, and seeds, and leave 20% for flexibility.

3. Consistency beats perfection.
   The “best” diet is the one you can stick to long-term without feeling restricted.

Bottom Line

There’s no magic in cutting carbs or fats.
Fat loss comes down to calories, protein, and consistency, not diet labels.

So, instead of asking “Which is better?”, ask “Which suits me better?”
That’s the diet you’ll actually stick with, and the one that will get you results.

Hall KD, Guo J, Courville AB, Boring J, Brychta R, Chen KY, Darcey V, Forde CG, Gharib AM, Gallagher I, Howard R, Joseph PV, Milley L, Ouwerkerk R, Raisinger K, Rozga I, Schick A, Stagliano M, Torres S, Walter M, Walter P, Yang S, Chung ST. Effect of a plant-based, low-fat diet versus an animal-based, ketogenic diet on ad libitum energy intake. Nat Med. 2021 Feb;27(2):344-353. doi: 10.1038/s41591-020-01209-1. Epub 2021 Jan 21. PMID: 33479499.