Randomised Controlled Trials (RCTs)

Comparing Low-Carb Diets Of Less Than 130g Carbohydrate Per Day To Low-Fat Diets Of Less Than 35% Fat Of Total Calories

Why are randomised controlled trials important?

Currently, a lot of nutrition science is based on observational data through epidemiology, which presents association but not causation. Randomised controlled trials (RCTs) are the gold standard in evidence because they help establish cause and effect. When looking at nutrition science it’s important to acknowledge whether a study is based on association or causation. In addition, the RCTs referenced below vary in duration from 30 days to 2 years. For a table of all the RCTs which were longer than 12 months in duration please click here.

Key
^ = Greater Weight Loss, * = Significantly Greater Weight Loss Between Groups

Time Frame & Links	Low-Carb (LC) Weight Loss	Low-Fat (LF) Weight Loss	Participants (LC v LF)
1) 6 Months	8.5kg^*	3.9kg	22 v 20
2) 12 Months	4.3kg^	2.5kg	20 v 17
3) 6 Months	5.8kg^*	1.9kg	43 v 36
4) 12 Weeks	9.9kg^*	4.1kg	16 v 14
5) 12 Weeks	6.2kg^*	3.4kg	22 v 23
6) 24 Weeks	12.7kg^*	7.2kg	46 v 34
7) 30-50 Days	5.5kg^*	3.5kg	28 v 28
8) 10 Weeks	7.0kg^	6.8kg	15 v 16
9) 6 Weeks	6.2kg^	6.0kg	16 v 16
10) 6 Weeks	6.4kg^*	4.2kg	12 v 11
11) 3 Months	3.55kg^*	0.92kg	40 v 39
12) 12 Weeks	6.3kg^	5.3kg	49 v 47
13) 12 Months	4.7kg^*	2.2kg	68 v 61
14) 8 Week	7.8kg^*	6.4kg	48 v 45
15) 3 Months	6.9kg^*	2.1kg	10 v 10
16) 24 Weeks	11.1kg^*	6.9kg	21 v 29
17) 2 Years	5.5kg^*	3.3kg	83 v 94
18) 8 Weeks	7.5kg^*	6.2kg	52 v 47
19) 24 Weeks	11.9kg^	10.1kg	45 v 43
20) 12 Weeks	10.1kg^*	5.2kg	20 v 20
21) 12 Months	14.5kg^	11.5kg	33 v 36
22) 13 Weeks	13.2kg^*	7.3kg	18 v 15
23) 24 Months	2.34kg	2.97kg^	31 v 30
24) 3 Months	5.5kg^*	2.6kg	15 v 18
25) 12 Months	5.6kg^*	1.4kg	59 v 60
26) 4 Months	9.79kg^*	6.14kg	20 v 20
27) 8 Weeks	8.4kg^*	6.7kg	32 v 28
28) 12 Months	3.1kg	3.1kg	47 v 49
29) 2 Years	6.34kg	7.37kg^	154 v 153
30) 24 Months	1.5kg^	0.2kg	28 v 40
31) 12 Weeks	6.8kg^	5.2kg	18 v 15
32) 12 Weeks	8.0kg^*	6.4kg	24 v 21
33) 1 Year	13.7kg	13.7kg	55 v 51
34) 1 Year	5.1kg^	3.1kg	62 v 64
35) 48 Weeks	11.37kg^	9.62kg	57 v 65
36) 3 Months	5.0kg^	3.7kg	63 v 66
37) 24 Weeks	12.0kg^	11.5kg	46 v 47
38) 6 Months	6.0kg^	5.9kg	57 v 174
39) 1 Year	2.1kg	3.0kg^	40 v 40
40) 6 Weeks	6.1kg^*	3.9kg	15 v 15
41) 24 Weeks	7.1kg^*	4.7kg	28 v 30
42) 3 Months	7.6kg^*	4.3kg	22 v 19
43) 6 Months	4.3kg^	4.0kg	29 v 30
44) 6 Months	2.6kg^	1.4kg	12 v 12
45) 8 Weeks	7.4kg^	6.5kg	12 v 12
46) 6 Months	6.8kg^	5.6kg	53 v 57
47) 3 Months	3.4kg	4.1kg^	150 v 150
48) 12 Months	11.8kg^*	6.9kg	55 v 55
49) 1 Year	2.9kg	3.7kg^	30 v 30
50) 6 Months	8.5kg^*	3.5kg	43 v 35
51) 52 Week	9.8kg	10.1kg^	41 v 37
52) 6 Months	9.1kg^	8.9kg	25 v 24
53) 6 Months	8.0kg^	5.7kg	21 v 17
54) 6 Months	1.6kg^*	0.6kg	30 v 32
55) 4 Months	14.7kg^*	5.05kg	45 v 40
56) 12 Weeks	11.9kg	12.2kg^	20 v 18
57) 32 Weeks	12.7kg^*	3.0kg	12 v 13
58) 18 Months	5.0kg^	2.4kg	32 v 33
59) 10 Weeks	25.8kg^*	2.08kg	10 v 10
60) 12 Months	7.9kg^*	1.7kg	16 v 18
61) 2 Years	6.8kg^	6.6kg	33 v 28
62) 12 Months	6.0kg^	5.3kg	304 v 305
63) 12 Weeks	9.5kg^*	2.0kg	21 v 12
64) 12 Weeks	13.72kg^*	0.77kg	46 v 45
65) 18 Months	2.76kg^*	0.71kg	43 v 42
66) 8 Weeks	5.9kg^*	0.9kg	19 v 15
67) 12 Months	9.3kg^*	5.8kg	76 v 64
68) 6 Months	5.1kg^*	0.2kg	49 v 22
69) 12 Weeks	10.4kg^*	+0.5kg	98 v 90
70) 6 Months	4.1kg^	1.0kg	60 v 61
71) 4 Months	8.8kg^*	4.7kg	45 v 49
Results:	62/71 LC Are > LF	7/71 LF Are > LC	3030(LC) v 2062(LF)
	39/71 LC Are Sig.	0/71 LF Are Sig.	2 RCTs Are Equal

Please note: Longer trials are considered more robust but are expensive. Short term studies may not allow sufficient time for participants to adapt to the diet or demonstrate durability of results but are useful to identify trends to guide future research.