Table 1.

High-fat diet and human diabetes intervention studies.

Diet	Participants	Duration	Findings	References
Randomized controlled intervention trials (RCTs)
50 E % carbohydrate, 20 E % protein, 5 E% PUFAs SFA: 20 E% SFAs, 5 E% MUFAs cis-MUFA: 20 E% cis-MUFAs, 5 E% SFAs trans MUFA: 20 E% trans-MUFAs, 5 E% SFAs	Obese type 2 diabetes patients aged 42–58 (N = 16)	6 weeks	No difference in postprandial glucose and serum lipids; increased serum insulin and C-peptide for SAT and trans MUFA diets	[67]
45 E% carbohydrate, 15 E% protein Saturated fat diet (butter and margarine) Monounsaturated fatty acid diets (oleic acid)	Healthy people aged 30–65 (N = 162)	3 months	Insulin sensitivity was significantly impaired for SAT diet, while there was no difference for MUFA diet	[68]
Control group: regular diet Intervention group: carbohydrate >50 E%, fat <30 E%	Overweight people aged >40 with glucose tolerance (7.8–11.1) mmol/l (N = 102)	3.1 years	55% reduction in the incidence of diabetes in the intervention group	[69]
Cohort
Fat intake (total, SFA, MUFA, and PUFA)	Healthy people aged 40–69 (N = 1173)	2 years	Total fat is negatively associated with insulin sensitivity	[70]
Fat intake (SFA, MUFA, PUFA, TFA, long-chain omega-3 PUFA, and animal and vegetable fat)	Healthy women aged 45–50 (N = 35,988)	11 years	Diabetes incidence is negatively associated with vegetable fats	[71]
Fat intake (total fat, SAT, MUFA-oleic acid, PUFA-linoleic acid)	Healthy men aged 40–75 (N = 42,504)	12 years	Total fat and SAT intake are associated with a higher risk of type 2 diabetes	[72]
Foods high in fat (vegetable oils, butter, margarine, nuts and seeds, and cakes and biscuits)	European Prospective Investigation into Cancer (N = 340,234)	9 years	Margarine consumption is positively associated with diabetes risk	[73]
Fat intake (SFA, MUFA, PUFA, TFA, animal fats, vegetable fats, marine omega-3 fatty acids, non-marine omega-3 fatty acids, and omega-6 linoleic acid (18:2n-6))	The people who were free of diabetes but were at high cardiovascular risk were aged 55–80 (N = 3349)	4.3 years	SAT and animal fats (cheese and butter) are associated with a higher risk of diabetes	[74]
Fat intake (SFA, MUFA, and PUFA)	Healthy women aged 45–50 (N = 8370)	6 years	Intake of MUFA, total n-3 PUFA, α-linolenic acid, and n-6 PUFA were positively associated with the incidence of diabetes	[75]
Total fat, SFA, MUFA, PUFA, and TFA	Healthy women aged 45–50 (N = 84,204)	14 years	TFA intake was positively associated with the risk of diabetes, while PUFA intake was negatively associated with the direction of diabetes	[76]
Type of fat and amount of fat: oils and margarine used during cooking and at the table	Healthy women aged 30–55 (N = 83,648)	32 years	Higher intakes of linoleic acid are associated with a lower risk of type 2 diabetes	[77]
	Healthy women aged 25–44 (N = 88,610)	22 years
	Healthy men aged 40–75 (N = 41,771)	26 years
Consumption of nuts and peanut butter (monounsaturated and polyunsaturated fatty acids)	Healthy women aged 35–49 (N = 83,818)	16 years	Women who ate nuts or peanut butter at least five times a week had a lower risk of developing diabetes	[78]