Diets
ketogenic diet decreases body weight
In plain terms: Is keto better than low-fat for losing weight?
Part of: 🥗 ketogenic diet
Probably yes for short-term loss, but it is not superior once calories and protein are matched.
📅 Last reviewed: 2026-07-15 ⓘ
Evidence ladder
How far up the ladder this claim has climbed. A high consensus on a low rung means "consistent so far," not "proven in people."
Top evidence so far: All trials, pooled (Meta-analysis)
How the studies fall
What the evidence shows
Carbohydrate restriction does NOT beat low-fat for weight when diet quality/protein/calories are accounted for - the 'carbohydrate-insulin / metabolic-advantage' framing is unsupported. (Keto does cause real short-term weight loss vs baseline; it just isn't superior.)
The evidence (12)
| Source | Grade | Stance | Quality | Finding |
|---|---|---|---|---|
| Tobias 2015 · Lancet Diabetes Endocrinol | meta-analysis | supports | high | Meta-analysis of RCTs: low-fat not superior; low-carb produced significantly greater long-term weight loss than low-fat. |
| Stern 2004 · Ann Intern Med | RCT | contradicts | moderate | 1-yr severe obesity: weight loss similar between low-carb and conventional diet despite 6-mo low-carb advantage. [DIRECTIONAL-NULL temper 2026-07-15: well-powered no-difference REFUTES a superiority claim -> contradicts, not tested-null] ↩ SUPERSEDED — pooled in the review above, counted once |
| Hu T, et al. (Bazzano) 2012 · Am J Epidemiol | meta-analysis | contradicts | high | MA 23 RCTs n=2788: weight/waist reductions NOT significantly different LCD vs LFD [DIRECTIONAL-NULL temper 2026-07-15: well-powered no-difference REFUTES a superiority claim -> contradicts, not tested-null] |
| Gardner 2007 · JAMA | RCT | supports | high | A TO Z trial: Atkins (low-carb) yielded greatest 12-mo weight loss vs Zone/Ornish/LEARN in overweight women. ↩ SUPERSEDED — pooled in the review above, counted once |
| Gardner CD, et al. (DIETFITS) 2018 · JAMA | RCT | contradicts | high | RCT n=609 12mo: healthy-LC -5.3kg vs healthy-LF -6.0kg, NS; insulin-secretion 'responder' hypothesis failed [DIRECTIONAL-NULL temper 2026-07-15: well-powered no-difference REFUTES a superiority claim -> contradicts, not tested-null] |
| Sacks 2009 · N Engl J Med | RCT | contradicts | high | POUNDS LOST: weight loss similar regardless of fat/protein/carbohydrate composition; macronutrient ratio not decisive over 2y. ↩ SUPERSEDED — pooled in the review above, counted once |
| Brehm 2003 · J Clin Endocrinol Metab | RCT | supports | moderate | VLC diet produced greater 6-mo fat/weight loss than calorie-restricted low-fat in healthy obese women. ↩ SUPERSEDED — pooled in the review above, counted once |
| Samaha 2003 · N Engl J Med | RCT | supports | moderate | Severe obesity: low-carb greater 6-mo weight loss (-5.8 vs -1.9kg) and better triglycerides/insulin sensitivity than low-fat. |
| Shai 2008 · N Engl J Med | RCT | supports | high | DIRECT 2-yr RCT: low-carb produced greater weight loss (-4.7kg) than low-fat (-2.9kg) and improved lipids. ↩ SUPERSEDED — pooled in the review above, counted once |
| Bueno 2013 · Br J Nutr | meta-analysis | supports | moderate | MA of 13 RCTs >=12mo: VLCKD gave modestly greater long-term weight loss (~0.9 kg) than low-fat |
| Foster 2010 · Ann Intern Med | RCT | contradicts | high | 2-yr trial: low-carb and low-fat produced similar weight loss; early low-carb advantage attenuated by 24 months. [DIRECTIONAL-NULL temper 2026-07-15: well-powered no-difference REFUTES a superiority claim -> contradicts, not tested-null] |
| Foster 2003 · N Engl J Med | RCT | mixed | moderate | Low-carb greater weight loss at 6 mo but difference not significant at 12 mo; early advantage not durable. |
Disagree, or know a study we missed?
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