With regard to health, saturated fat is most looked at for its perceived influence on heart disease through interacting with cholesterol and plasma triglycerides.
Several meta-analysis have been carried out on saturated fat and the perceived risk of heart health.
In these meta-analyses, there’s scant evidence that saturated fat increases risk for Cardiovascular Diseases. However, replacing some saturated fat with polyunsaturated may indeed reduce risk.[2]
Studies on epidemiology find relative risk ratios (RRs) close to a value of 1, which is zero effect. So there doesn’t seem to be a strong relationship between saturated fat intake and risk for various conditions such as Cardiovascular Disease, Stroke, and Coronary Heart Disease.[3][4]
Effects on cholesterol levels
Saturated fats do increase cholesterol levels relative to polyunsaturated fats.[2][8] Of course in any study done on macronutrients (fat, carbs, or protein) removal of a macronutrient needs to be replaced by another to balance calories out. Many studies replace saturated fats with polyunsaturated fats, which reduce cholesterol and triglyceride levels.[9][10][11][12]
This may lead to the conclusion that saturated fats raise them, when the possibility that they are inert is probably more realistic.[2]
Diets high in monounsaturated fats are also beneficial for certain parameters of heart health.[13]
Causation has not yet been placed on (dietary) cholesterol for causing heart problems. It is definitely correlated,[14][15] with the ratio of HDL cholesterol to Total cholesterol being the strongest predictor.[15]
The Brain
At least one study found that substituting dietary monounsaturated fatty acids with saturated fats via vegetable oils (40% fats overall, 16% of the chosen fat in each group) was associated with slightly more anger in participants, although this study also noted a spontaneous decrease in activity which may have contributed.[16]
Weight Gain – and Loss
Appetite
Food intake is usually behind weight gain or loss, so things that may modify food intake may also indirectly modify weight changes.
It’s now been found that fats per se are more effective than carbs and possibly proteins at increasing diet satiety after a meal.[19] When looking at what fats are consumed, saturated fats seem comparable to PUFAs (Polyunsaturated fatty acids) (but greater than MUFAs (monounsaturated fatty acids)) in increasing it [20] while other studies note either comparable effects[21] or an unreliable increase in saturated fat versus MUFA (no changes in whole day values, but following a meal there was a spike).[22]
Saturated fats either result in less food intake and appetite or they do not differ from unsaturated fats.
Physical Activity
Switching dietary MUFAs out for saturated fatty acids in otherwise healthy young adults appears to decrease spontaneous activity levels.[16]
Hormonal Effects
Androgens
It is known that diet interacts with androgen levels (known to be related to reduced androgen concentrations in vegetarians[23] and reduced androgen levels in cohorts with lower fat intakes[24]), which is thought to be related to dietary fat since putting men on a low-fat (high fiber) diet reduces circulating androgens[25] whereas the opposite exists as well (higher fat diet at 41% of calories, with a higher intake of saturated fat, increasing testosterone).[26] The magnitude of these changes is a low fat diet reducing testosterone in older men by 12%[25] and an increase in dietary fat in young men increasing testosterone by 13%.[26]
There may be a slight suppression of testosterone concentrations following ingestion of a high fat meal (fatty acids not specified)[27] which is thought to be related to chylomicrons and NEFAs (increase in serum by ingestion of dietary fat) may suppress LH-induced testosterone synthesis.[28]Elsewhere, androgen precursors have been noted to be increased without an increase in testosterone.[29]
Dietary fat in general (with a slight trend towards saturated fats) are now known to positively regulate testosterone and androgen production. The magnitude of changes, however, are fairly small (below 20%)
Scientific Support & Reference Citations
References
- Fats and Fatty Acids in Human Nutrition
- Mozaffarian D, Micha R, Wallace S Effects on coronary heart disease of increasing polyunsaturated fat in place of saturated fat: a systematic review and meta-analysis of randomized controlled trials . PLoS Med. (2010)
- Kromhout D, et al The confusion about dietary fatty acids recommendations for CHD prevention . Br J Nutr. (2011)
- Siri-Tarino PW, et al Meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease . Am J Clin Nutr. (2010)
- Scarborough P, et al Meta-analysis of effect of saturated fat intake on cardiovascular disease: overadjustment obscures true associations . Am J Clin Nutr. (2010)
- Katan MB, et al Saturated fat and heart disease . Am J Clin Nutr. (2010)
- Stamler J Diet-heart: a problematic revisit . Am J Clin Nutr. (2010)
- Dietary lipids and blood cholesterol: quantitative meta-analysis of metabolic ward studies
- Woodside JV, McKinley MC, Young IS Saturated and trans fatty acids and coronary heart disease . Curr Atheroscler Rep. (2008)
- Wang Q, et al Effect of omega-3 fatty acids supplementation on endothelial function: A meta-analysis of randomized controlled trials . Atherosclerosis. (2012)
- Colussi G, et al Omega-3 fatty acids: from biochemistry to their clinical use in the prevention of cardiovascular disease . Recent Pat Cardiovasc Drug Discov. (2007)
- Mozaffarian D, Wu JH Omega-3 fatty acids and cardiovascular disease: effects on risk factors, molecular pathways, and clinical events . J Am Coll Cardiol. (2011)
- Schwingshackl L, Strasser B, Hoffmann G Effects of monounsaturated fatty acids on cardiovascular risk factors: a systematic review and meta-analysis . Ann Nutr Metab. (2011)
- Huxley R, Lewington S, Clarke R Cholesterol, coronary heart disease and stroke: a review of published evidence from observational studies and randomized controlled trials . Semin Vasc Med. (2002)
- Prospective Studies Collaboration, et al Blood cholesterol and vascular mortality by age, sex, and blood pressure: a meta-analysis of individual data from 61 prospective studies with 55,000 vascular deaths . Lancet. (2007)
- Kien CL, et al Substituting dietary monounsaturated fat for saturated fat is associated with increased daily physical activity and resting energy expenditure and with changes in mood . Am J Clin Nutr. (2013)
- Karra E, Chandarana K, Batterham RL The role of peptide YY in appetite regulation and obesity . J Physiol. (2009)
- le Roux CW, Bloom SR Peptide YY, appetite and food intake . Proc Nutr Soc. (2005)
- Lomenick JP, et al Effects of meals high in carbohydrate, protein, and fat on ghrelin and peptide YY secretion in prepubertal children . J Clin Endocrinol Metab. (2009)
- Kozimor A, Chang H, Cooper JA Effects of dietary fatty acid composition from a high fat meal on satiety . Appetite. (2013)
- Effect of fat saturation on satiety, hormone release, and food intake
- Cooper JA, et al Impact of exercise and dietary fatty acid composition from a high-fat diet on markers of hunger and satiety . Appetite. (2011)
- Bélanger A, et al Influence of diet on plasma steroids and sex hormone-binding globulin levels in adult men . J Steroid Biochem. (1989)
- Hill P, et al Diet and urinary steroids in black and white North American men and black South African men . Cancer Res. (1979)
- Wang C, et al Low-fat high-fiber diet decreased serum and urine androgens in men . J Clin Endocrinol Metab. (2005)
- Dorgan JF, et al Effects of dietary fat and fiber on plasma and urine androgens and estrogens in men: a controlled feeding study . Am J Clin Nutr. (1996)
- Meikle AW, et al Effects of a fat-containing meal on sex hormones in men . Metabolism. (1990)
- Meikle AW, et al Nonesterified fatty acids modulate steroidogenesis in mouse Leydig cells . Am J Physiol. (1989)
- Mai K, et al Free fatty acids increase androgen precursors in vivo . J Clin Endocrinol Metab. (2006)
