Low-fat diet

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USDA's Food Pyramid
New Version of the Food Guide Pyramid[1]

A low-fat diet is one that restricts fat and often saturated fat and cholesterol as well. Low-fat diets are intended to reduce diseases such as heart disease and obesity, but have instead been shown to be a causal factor of obesity.[2] Reducing fat in the diet can make it easier to cut calories. Fat provides nine calories per gram while carbohydrates and protein each provide four calories per gram, so choosing low-fat foods makes it possible to eat a larger volume of food for the same number of calories. The Institute of Medicine recommends limiting fat intake to 35% of total calories to help prevent obesity and to help control saturated fat intake.[3]

Evidence[edit]

Low-fat vegan diets have been shown to reduce weight and cholesterol levels. In an analysis controlling for medication changes, a low-fat vegan diet appeared to improve glycemia and plasma lipids more than a conventional diabetes diet did.[4]

Reducing total fat intake leads to reductions in caloric intake, resulting in weight loss or less weight gain.[5] The overall benefit is small but beneficial.[6] With respect to weight loss low-fat diets do not appear to differ from other diets that also reduce overall calories.[7][8]

Low-fat diets have been promoted for the prevention of heart disease. Lowering fat intake from 35-40% of total calories to 15-20% of total calories has been shown to decrease total and LDL cholesterol by 10 to 20%; however, most of this decrease is due to a reduction in saturated fat intake.[9] Saturated fat has been shown to raise total and LDL cholesterol in a large number of studies[10] and has also been correlated with a higher risk of heart disease.[11]

A 2013 meta-analysis of randomized controlled trials of low- and high-fat diets showed low-fat diets decreased total cholesterol and LDL, but these decreases were not found when only considering low-calorie diets. It also showed HDL increases and triglyceride decreases in high-fat diets. Furthermore, lower total cholesterol was associated with lower intake of saturated fat and higher intake of polyunsaturated fat, HDL increases were associated with high monounsaturated fat intake and triglycerides associated with high carbohydrate intake. Decrease in saturated fat intake was only marginally related to decrease in LDL cholesterol. The meta-analysis concluded that neither high-fat nor low-fat diets could be unequivocally recommended.[12]

According to the National Academies Press, a high-fat diet can contain "unacceptably high" amounts of saturated fat, even if saturated fats from animal products and tropical oils are avoided. This is because all fats contain some saturated fatty acids. For example, if a person chose fats with only 20% saturated fatty acids, setting fat intake at 35% of total calories would mean that 7% of calories would come from saturated fat. For this reason, the Institute of Medicine recommends consuming no more than 35% of calories from fat.[13]

The influence of carbohydrates on body fat[edit]

Notwithstanding the impact of fat intake in plasma levels of fats, the proportion of carbohydrates in diet also has a strong influence on plasma levels of triglycerides and cholesterol. While a gradual increase in the carbohydrate content of the diet prevents hypertriglyceridemia,[14] a sudden increase has been shown to raise plasma triglycerides.[9] In agreement with this observation, a randomized trial comparing a low-carbohydrate diet (<40 g/day) and a low-fat diet (<30% of daily energy intake from total fat [<7% saturated fat]) revealed that low-carbohydrate diet was more effective at reducing fat mass, total-HDL cholesterol ratio, and triglycerides level.[15]

References[edit]

  1. ^ "MyPyramid". USDA. Archived from the original on April 23, 2011. Retrieved April 23, 2011.
  2. ^ Fogelholm, Mikael; Anderssen, Sigmund; Gunnarsdottir, Ingibjörg; Lahti-Koski, Marjaana (13 August 2012). "Dietary macronutrients and food consumption as determinants of long-term weight change in adult populations: a systematic literature review". Food & Nutrition Research. 56 (1): 19103. doi:10.3402/fnr.v56i0.19103. Retrieved 27 November 2017.
  3. ^ Makris A, Foster GD (December 1, 2002). "Dietary Approaches to the Treatment of Obesity". Psychiatr Clin North Am. 34: 813–27. doi:10.1016/j.psc.2011.08.004. PMC 3222874. PMID 22098806.
  4. ^ Barnard, Neal D; Cohen, Joshua; Jenkins, David JA; Turner-McGrievy, Gabrielle; Gloede, Lise; Green, Amber; Ferdowsian, Hope (May 2009). "A low-fat vegan diet and a conventional diabetes diet in the treatment of type 2 diabetes: a randomized, controlled, 74-wk clinical trial1234". The American Journal of Clinical Nutrition. 89 (5): 1588S–1596S. doi:10.3945/ajcn.2009.26736H. ISSN 0002-9165. PMC 2677007. PMID 19339401.
  5. ^ Food and nutrition board, institute of medicine of the national academies (2005). Dietary reference intakes for energy, carbohydrate, fiber, fat, fatty acids, cholesterol, protein, and amino acids (macronutrients). National Academies Press. pp. 774–777.
  6. ^ Hooper, L; Abdelhamid, A; Moore, HJ; Douthwaite, W; Skeaff, CM; Summerbell, CD (Dec 6, 2012). "Effect of reducing total fat intake on body weight: systematic review and meta-analysis of randomised controlled trials and cohort studies". BMJ (Clinical research ed.). 345: e7666. doi:10.1136/bmj.e7666. PMC 3516671. PMID 23220130.
  7. ^ Pirozzo, S; Summerbell, C; Cameron, C; Glasziou, P (2002). "Advice on low-fat diets for obesity". The Cochrane Database of Systematic Reviews (2): CD003640. doi:10.1002/14651858.CD003640. PMID 12076496.
  8. ^ Strychar, I (Jan 3, 2006). "Diet in the management of weight loss". CMAJ : Canadian Medical Association Journal. 174 (1): 56–63. doi:10.1503/cmaj.045037. PMC 1319349. PMID 16389240.
  9. ^ a b Lichtenstein AH; Van Horn L (1998). "Very low fat diets". Circulation. 98: 935–939. doi:10.1161/01.cir.98.9.935.
  10. ^ Food and nutrition board, institute of medicine of the national academies (2005). Dietary reference intakes for energy, carbohydrate, fiber, fat, fatty acids, cholesterol, protein, and amino acids (macronutrients). National Academies Press. p. 482.
  11. ^ Food and nutrition board, institute of medicine of the national academies (2005). Dietary reference intakes for energy, carbohydrate, fiber, fat, fatty acids, cholesterol, protein, and amino acids (macronutrients). National Academies Press. p. 483. Archived from the original on 2014-05-28.
  12. ^ Schwingshack, Lukas; Hoffmann, Georg (Oct 17, 2014). "Comparison of effects of long-term low-fat vs high-fat diets on blood lipid levels in overweight or obese patients: a systematic review and meta-analysis". Journal of the Academy of Nutrition and Dietetics. Elsevier Inc. (published Dec 2013). 113 (12): 1640–61. doi:10.1016/j.jand.2013.07.010. PMID 24139973.
  13. ^ Food and nutrition board, institute of medicine of the national academies (2005). Dietary reference intakes for energy, carbohydrate, fiber, fat, fatty acids, cholesterol, protein, and amino acids (macronutrients). National Academies Press. p. 799.
  14. ^ Ullmann D, Connor WE, Hatcher LF, Connor SL, Flavell DP (1991). "Will a high-carbohydrate, low-fat diet lower plasma lipids and lipoproteins without producing hypertriglyceridemia?". Arterioscler Thromb. 11: 1059–1067. doi:10.1161/01.atv.11.4.1059.
  15. ^ Bazzano, Lydia A. (2014). "Effects of Low-Carbohydrate and Low-Fat Diets: A Randomized Trial". Annals of Internal Medicine. 161 (5): 309–318. doi:10.7326/M14-0180. PMC 4428290.

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