Ideas about the role of dietary fat in weight loss have undergone considerable transformation during the 1990s and early 2000s. A shift of thinking that diverges from the theory that a low-fat or no-fat diet is beneficial for cardiovascular health and weight loss. As of 2010, a mounting body or research indicates the importance of dietary fat for overall good health and effective weight loss. Furthermore, scientific evidence points to the importance of eating specific kinds of fats, like omega-3 fatty acids, say "The Omega Diet," authors Artemis Simopoulos and Jo Robinson.
Omega-3 Fatty Acids
Your body cannot make omega-3 fatty acids, so you must gain them through diet. However, only 40 percent of Americans eat enough omega-3s, and 20 percent have omega-3 levels so low they cannot be detected, note Simopoulos and Robinson. Omega-3s are important because they instruct genes to produce less of an enzyme that is needed for fat production, the authors note. In addition, if dietary fat is absent, the body manufactures its own fat, which is an unhealthy type of fat. Eating sufficient quantities of good fat helps prevent this. Simopoulos and Robinson advocate reducing intake of omega- 6 fatty acids and saturated fats, as well as eating 7 g omega-3 fatty acids a week. Sources of omega-3s include cold-water fatty fish like salmon, walnuts and olive oil. Foods high in omega-6s include most vegetable oils other than canola as well as foods that contain such oils, such as tortilla chips or mayonnaise. Saturated fats occur in meat, dairy, nuts and tropical oils.
Insulin and Leptin Resistance
Insulin, produced by the pancreas, is released right after sugars enter the blood stream. Leptin is a hormone produced by fat tissue. Both affect the brain's hypothalamus and act as appetite depressors. A 2009 study in the "Journal of Clinical Investigation" showed that after three days on a diet high in saturated fat, brains of rats and mice developed insulin and leptin resistance. Animals fed a monounsaturated fatty acid, oleic acid, did not have insulin or leptin resistance, says lead study author Stephen Benoit.
Lessened Cardiovascular Risk
You can lose the same amount by consuming a moderate-fat diet versus a low-fat diet, but you are more likely to improve your cardiovascular risk profile with a proper moderate-fat diet, says Christine Pelkman, lead author for a study published in the 2004 "American Journal of Clinical Nutrition." A 2010 study in the "Canadian Medical Association Journal" also points to the benefits of consuming "good" fats. The study examined effect of high- versus low-monounsaturated-fat diets in patients with high blood cholesterol and triglycerides. This research shows that high-monounsaturated-fat diets increase healthy HDL cholesterol, lowering cardiovascular risk, says lead study author David Jenkins.
Lean Mass Preservation
In a 2004 study on women with and without type 2 diabetes that appeared in "The Journal of Nutrition," lead researcher Peter Clifton found that the group assigned to a low-fat diet showed adverse effects on body fat distribution when compared to the group assigned to a high-monounsaturated-fat diet. Weight, total fat mass and regional fat mass loss did not differ between the two groups of non-diabetic women. However, in premenopausal women on the high monounsaturated fat diet, there was an apparent preservation of lean mass.
Fat Mobilization
The importance of dietary fat intake on mobilization of stored lipids and glucose in the liver was shown in a May 2005 "Cell Metabolism" study conducted by Manu Chakravarthy and colleagues. Dietary fat rather than stored body fat was needed to activate a protein called PPAR-alpha, which is responsible for taking energy from nutrients like fats and carbohydrates. PPAR-alpha, when activated by dietary fats such as omega-3s, may help mobilize stored body fat stored through pathways in your liver.
Thermogenesis by Brown Fat
Animals have two kinds of fat. Yellow fat stores excess lipids in peripheral body areas. Brown fat is responsible for thermogenesis, a heat-releasing reaction used when the body is cold and when excess calories are consumed. In other words, brown fat doesn't store calories, it burns them. In human adults, brown fat exists in small quantities in the neck and upper chest. In the book "Hunger Free Forever," Michael Murray and Michael Lyon discuss the importance of consuming monounsaturated fats like those in sesame oil as well as medium chain triglycerides such as in coconut oil, which have been shown to increase thermogenesis in brown fat.
References
- "The Omega Diet"; Artemis Simopoulos and Jo Robinson; 1999
- "Journal of Clinical Investigation"; Palmitic Acid Mediates Hypothalamic Insulin Resistance by Altering PKC-θ Subcellular Localization in Rodents; Stephen Benoit et al., September 2009
- "American Journal of Clinical Nutrition"; Effects of Moderate-fat (from monounsaturated fat) and Low-fat Weight-loss Diets on the Serum Lipid Profile in Overweight and Obese Men and Women; Christine Pelkman et al.; 2004
- "The Journal of Nutrition"; Very Low-Fat (12 percent) and High Monounsaturated Fat (35 percent) Diets Do Not Differentially Affect Abdominal Fat Loss in Overweight, Nondiabetic Women; Peter Clifton et al.; July 2004
- "Canadian Medical Association Journal"; Adding Monounsaturated Fatty Acids to a Dietary Portfolio of Cholesterol-lowering Foods in Hypercholesterolemia; David Jenkins et al.; November 2010
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