Low-Carb vs Low-Fat
Both approaches produce weight loss. The direct comparison in randomised trials shows modest differences — and the most rigorous trial suggests those differences may largely disappear when food quality and calories are matched.
Quick read · 4 min
- •Are deciding between a low-carb or low-fat approach and want to know what the trials show
- •Have seen conflicting headlines about carbs vs fat and want a clear answer
- •Are trying to find the right dietary approach for the long term
- •Both low-carb and low-fat diets produce weight loss — they work by creating a caloric deficit
- •In the most rigorous head-to-head trial (DIETFITS, 609 people), there was no significant difference in weight loss at 12 months
- •Low-carb may have a slight advantage in triglycerides and HDL; low-fat may lower LDL more
- •The best approach is the one you can actually maintain long-term — diet preference matters
Based on clinical trials · No rankings · Every claim linked to source
Last reviewed: March 2026
The DIETFITS trial — the most rigorous comparison
When participants in the healthy low-fat group and healthy low-carb group were both instructed to eat high-quality food, minimise processed foods, and eat to satiety, there was no significant difference in weight loss at 12 months between the two approaches. Both groups lost approximately 5–6 kg on average.
Meta-analysis data
Across 33 randomised controlled trials, low-carbohydrate diets produced 1.33 kg more weight loss than low-fat diets over 6–23 months. Low-carb also showed greater reductions in triglycerides, diastolic blood pressure, and higher HDL cholesterol.
Source: Frontiers in Nutrition 2022 [1]
What each approach offers
| Factor | Low-carb | Low-fat |
|---|---|---|
| Weight loss (6–12 months) | Slight advantage in meta-analysis (+1.33 kg) | Similar when food quality matched (DIETFITS) |
| Triglycerides | Greater reduction | Smaller reduction |
| LDL cholesterol | May increase (diet-dependent) | Tends to decrease |
| HDL cholesterol | Greater increase | Smaller increase |
| Blood sugar control | Faster initial improvement | Similar long-term |
Key caveats
- ⚠The weight loss difference in meta-analyses (~1.33 kg) is modest and may not be clinically meaningful for all individuals.
- ⚠Both approaches work primarily through caloric restriction — neither macronutrient is uniquely fattening or slimming.
- ⚠"Low-carb" and "low-fat" each encompass a broad range of diet quality. An ultra-processed low-fat diet performs differently to a whole-food low-fat diet.
- ⚠Adherence varies widely by individual preference, food culture, and lifestyle. The best diet is the one that can be sustained.