The information on this page has been compiled and edited from previously published articles, by Dr. Connie Guttersen.  The articles are not intended as health advice, nor do they necessarily reflect the views and opinions of the California Olive Committee. Always consult your physician on matters of health and wellness.

by Connie Guttersen, RD PhD.

It is interesting that in the 1960′s Ancel Keys’ Seven Countries Studies provided us with the initial insight that a low fat diet is not always the answer to a healthier heart. His studies also showed that when it comes to health, the type of fat plays a more important role than the amount of fat (such as the monounsaturated fats found in olives, nuts and olive oil or the omega 3 oils found in seafood, as compared to saturated fats or hydrogenated oils).

Well as I write this in 2006, one of the largest and most expensive studies in our time, The Women’s Health Initiative Dietary Modification Trial, indicates that low fat diets do not better prevent disease or improve weight loss. The eight year trial, published in the Journal of the American Medical Association, followed almost 50,000 women between the ages of 50 and 70 years who were randomly assigned to follow a low fat diet (20% of total calories) and then compared them to another group of women who continued with their usual diet. After eight years, the researchers looked at how many women in each group developed health problems. The results show that the women assigned to the low fat diet did not appear to gain protection against breast cancer, colorectal cancer, cardiovascular disease, and their body weights where similar to those women following their usual diets. The debate will most likely continue since some of the proposed limitations include that the level of fat in the diet was not low enough and should have been below 20% of total calories. (A dietary restriction that has been regarded  as difficult to follow for long periods of time.)  The other limitations being mentioned include that the women studied were not at an ideal age range, or perhaps the study should have continued for a longer period of time. Regardless, there will still be some discussion among the medical community as to how to apply these results to key messages for the American public.

These results may come as a surprise for many who have been hearing for years that reducing dietary fat in the diet is important for long term health and weight loss.  Yet, numerous studies have been proving this concept inaccurate. Studies such as the Nurses Health Study have consistently found little relation between the percentage of calories from fat and risks of breast cancer, colon cancer, or coronary heart disease. These studies, amongst others, have strongly influenced positive changes in dietary recommendations made by the USDA, US Dietary Guidelines Committee, and the US Institute of Medicine to advocate a greater emphasis on the type of fat consumed rather than the low fat approach.

Replacing saturated fat and trans unsaturated fats with monounsaturated and polyunsaturated fats is more effective in preventing coronary heart disease in women than reducing overall fat intake.

The following three sections on Heart Disease, Cancer and Obesity contain important studies, which substantiate key messages for why low fat diets are not always the cure all for these conditions. These studies can help health professionals emphasize the importance of choosing nutrient rich foods in a balanced diet and to communicate that the type of fat we eat is a more effective message than just focusing on the phrase, “low fat” as healthy.

Heart Disease

The conventional low fat diets have not been shown to be the best heart healthy approach. While they tend to reduce cholesterol, it is at the expense of a decreased level of high-density lipoproteins, and an increased level of triglycerides. On the other hand, a diet which contains a moderate amount of fat, primarily from the monounsaturated type, will decrease an elevated blood cholesterol and low density lipoproteins, and will also maintain the level of high density lipoproteins and lower the elevated triglyceride levels.

A recent study conducted by Harvard School of Public Health used a regression analysis of data from the Nurses Health Study (80,000 women for 14 years) suggests that replacing saturated fat and trans unsaturated fats with monounsaturated and polyunsaturated fats is more effective in preventing coronary heart disease in women than reducing overall fat intake. More recent information compares different sources of monounsaturated fats (olive oil, peanut oil, peanuts, peanut butter) to the American Heart Association: Step II cholesterol lowering diet (low fat, high carbohydrate). In this study, Etherton, et al. proposes that diets moderate in dietary fat, (35% of total calories) and primarily comprised of monounsaturated fat will lower total and low-density lipoprotein cholesterol to a degree similar to that of the Step II diet. Moreover, the monounsaturated studies had the added benefit of not decreasing high-density lipoprotein or increasing triglycerides, as the Step II diet did.  In this particular study, all the different monounsaturated sources contained similar amounts of oleic acid (77%).  Despite this, differences were seen in their individual ability to decrease cardiovascular risk. These differences in cardiovascular risk reduction among the different types of monounsaturated foods may be attributed to additional components such as antioxidants and phytochemicals which were present prior to refinement.

Further review of the research finds protective qualities, such as antioxidants naturally found in olives, nuts, and olive oil.

Cancer

A recent study by Trichopoulou, published in Cancer Epidemiology, Biomarkers and Prevention, confirmed a lower incidence of cancer, particularly for the breast, colon and prostate in the Mediterranean countries. The current study calculated that up to 25% of the incidence of colorectal cancer, 15% of breast cancer, and 10% of prostate cancer could be prevented if populations of highly developed western countries would shift to the traditional healthy Mediterranean diet. In conclusion, the Mediterranean diet could reduce the overall incidence of cancer in Northern Europe and North America by up to 10%.

Although total fat intake has been unrelated to breast cancer risk in prospective epidemiologic studies, there is some evidence that the type of fat may be important. In data based on the detailed food frequency questionnaire administered in the Nurses Health Study, an inverse relationship between monounsaturated fat and breast cancer was present. This is an intriguing observation as we’re aware of the relatively low rates of breast cancer in Southern European countries which have high average intakes of monounsaturated fat in their diets from nuts, olives, and olive oil.  In case controlled studies in Spain and Greece, women who used more olive oil had reduced risks of breast cancer.  Further review of the research finds protective qualities, such as antioxidants naturally found in olives, nuts, and olive oil.

Obesity

The rate of obesity and its associated co-morbidities, referred to as Metabolic Syndrome, is at an all time high, as is the rate of weight recidivism, or failure to maintain weight loss– which is at approximately 90% after 18 months. This high failure rate is related to non-appetizing foods, poor adherence as a lifestyle, and metabolic responses to extreme dieting regimens. The conventional approach to dieting has been to focus on low fat approaches, which tend to result in a higher carbohydrate intake. Today’s research is finding that the best approach is one which emphasizes a moderate intake of the best types of carbohydrate, such as whole grains balanced with lean meats, fruits, vegetables, and a moderate intake of the healthiest sources of dietary fats. This type of diet not only addresses the improvement of the symptoms associated with Metabolic Syndrome, which benefits from moderate levels beneficial dietary fats, but it adds a dimension of palatability from the moderate amounts of fat which make the plan easier to adopt as an enjoyable way of eating.

An enlightening study, which has preceded many important discussions and ways of looking at how we treat obesity, was led by Brigham and Women’s Hospital and Harvard School of Public Health, published in the International Journal of Obesity. The long-term weight loss research evaluated and compared two calorie controlled diets, one moderate in fat, based on the Mediterranean diet, and the other a low fat diet.  After one year, only 27% of the low fat group was still participating as compared to 58% in the moderate fat group.  In conclusion, after 18 months, the moderate fat group had better results than the low fat group, which had regained their body weight and ended the study with a net increase of body weight. The study also concluded that better results were seen in the moderate fat group because they enjoyed more flavorful foods and were less likely to drop out of treatment. The moderate fat group also increased their daily fiber intake and vegetable consumption as compared to the low fat group.  Dietary fat, primarily from monounsaturated sources, enhanced the flavor of the meals, especially for vegetables and also provided satiety.

A separate but related issue involves the consequences of dieting, in particular, dieting with a low fat diet and/or by caloric restriction alone. It is conceivable that dieting provokes stress, anxiety and even depression. However, recent studies conclude that these feelings may also be related to the actual amount and type of fat consumed and that a low fat diet (approximately 25% of total caloric intake from fat or less) does indeed promote the symptoms of depression. Dieting and weight cycling decreases serotonin levels by decreasing the blood levels of the amino acid precursor, tryptophan. Dieting also results in alterations or depletion of total membrane essential fatty acids, such as omega 3 fatty acids. The change in the membrane distribution of fatty acids alters the balance of saturated, monounsaturated, omega 3 and omega 6 levels–a situation which potentially leads to a neurochemical imbalance that is conducive to depression. These compositional changes in membrane properties directly influence the activity of the neurotransmitter serotonin.

These studies provide health experts with an expanded definition of “healthy eating” which can be used to develop a more detailed and global approach for communicating key messages. The message is that the overall diet or the combination/balance of foods is more important than any one food type alone. It is also to say that the Mediterranean cuisine is not the only one that reflects this way of eating; other healthy cuisines include traditional diets from Latin American and Asia.  Today’s food professional is using flavor profiles from these cuisines to expand the choices of foods we enjoy in our healthy diets.

REFERENCES:

• Prentice RL, Caan B, Chlebowski RT, et al. Low-fat dietary pattern and risk of invasive breast cancer: the Women’s Health Initiative Randomized Controlled Dietary Modification Trial. JAMA 2006; 295:629-42.
• Beresford SA, Johnson KC, Ritenbaugh C, et al. Low-fat dietary pattern and risk of colorectal cancer: the Women’s Health Initiative Randomized Controlled Dietary Modification Trial. JAMA 2006; 295:643-54.
• Howard BV, Van Horn L, Hsia J, et al. Low-fat dietary pattern and risk of cardiovascular disease: the Women’s Health Initiative Randomized Controlled Dietary Modification Trial. JAMA 2006; 295:655-66.
• Howard BV, Manson JE, Stefanick ML, et al. Low-fat dietary pattern and weight change over 7 years: the Women’s Health Initiative Dietary Modification Trial. JAMA 2006; 295:39-49.
• Etherton, P, et al High monounsaturated fatty acid diets lower both plasma cholesterol and triacylglycerol concentrations Am J Clin Nutr 1999;70:1009-15
• Trichopoulou A, et al Cancer and Mediterranean dietary traditions. Cancer Epidemiol Biomarkers Prev 2000; 9:869 -73
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• Keys A. Seven Countries: A multivariate analysis of death and coronary heart disease. Cambridge, MA. Harvard University Press, 1980
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• Wells As, Read NW, Laugharne JDE., Ahlumalia, NS. Alterations in mood after changing to a low fat diet. Br. J Nutr 1998;79: 23-30.