Nutrition and Obesity: Are Misguided Dietary Guidelines a Contributing Factor?
Background: Why the Low-Fat Diet
We often discuss the macronutrients protein, fat, and carbohydrates; with protein and carbs at 4 calories per gram and fats at 9 calories per gram. If we look at restricting the diet based on food grams, limiting fat grams has been the classical low-fat diet to cutting calories and weight. [There are some important nuances; for instance, protein and medium-chain triglycerides (e.g., lauric acid, the saturated fat in coconut oil) have thermogenic effects. Proteins require more digestive processing, using about 10% of caloric intake, and MCT's are readily converted to energy for metabolism.]
Fats are primarily categorized as monounsaturated (MUFA), polyunsaturated (PUFA), and saturated fats. Monounsaturated fats (e.g., olive oil) tend to lower LDL (bad cholesterol), polyunsaturated fats tend to lower both LDL and HDL (good cholesterol). Saturated fats tend to raise both LDL and HDL. (The relationship between saturated fat and HDL is in dispute.) Polyunsaturated fats can further be subdivided into Omega-3 (n-3) and Omega-6 (n-6). These are considered essential fatty acids, i.e., our bodies do not manufacture them and hence depend on dietary sources. Omega-3 fatty acids, which tend to be understated in the American diet, are found in cold-water fish (DHA/EPA, e.g., in salmon and sardines), and certain plant forms (ALA, in flaxseed and walnuts); relevant benefits include better brain function, favorable cardiovascular characteristics (eg., anti-inflammatory and anti-coagulant), and some protection from certain cancers. Omega-6 fats include most vegetable oils and shortening, typically overstated in the American diet; they are generally considered inflammatory but promote healthy hair, skin, and nails and help regulate hormonal and emotional balance. Omega-3 and Omega-6 fatty acids interact with each other, so a proper balance is important.
In particular, saturated fat has been the focus of much debate; some studies show a significant relationship between a high saturated fat diet and coronary heart disease/stroke and atherosclerosis (hardening of the arteries) or between saturated fat and cholesterol (also considered linked to coronary heart disease). Enig and Fallon, however, note that the American diet at the turn of the twentieth century (when CHD was not a significant public health issue) was much higher in consumption in animal saturated fats (e.g., butter, tallow and lard); the primary American dietary shift in the early twentieth century, was from animal fats to vegetable oils, shortening and hard margarine. (Dr. Enig, I note with amusement, refers to her food industry and enabling government bureaucrats and establishment critics as "dictocrats". She makes a compelling case of academic politics and pervasive bureaucratic groupthink.)
Among other things, Enig has focused on dangerous trans fats (which have a double whammy of raising bad cholesterol and lowering good cholesterol); her dissertation suggested that trans fats impede the effectiveness of enzymes in dealing with carcinogens. [Trans fats are generated in the process of hydrogenating heat-unstable (primarily Omega-6) vegetable oils, which enables baking and improves food product shelf life; deep-frying with partially hydrogenated vegetable shortening, a staple for many fast-food restaurants, is another important dietary source.] She also cites a long list of studies of adverse affects related to vegetable oil consumption (for example, one 1994 study reported about three-quarters of an artery clog was unsaturated fats, and other studies mention adverse affects on mineral or Omega-3 metabolism).
One of the relevant points of discussion is the ratio of Omega-6 to Omega-3 polyunsaturated fats in the diet. Iin a more natural food setting, this is roughly 2:1; in a more contemporary diet, this ratio can range from nearly 10-20:1.
What comes to mind is the old adage: "you are what you eat". We see this clearly from examples in egg and meat production. Many "free-range" hens or hens fed (high Omega-3) flaxseed meal produce eggs higher in vitamin E and lower in calories and fats. In finishing animals (fattening them up for butchery), cattle have often been fed Omega-6 feed (e.g., corn and soybeans, which have certain thyroid-suppressing effects) Farmers also discovered when they added coconut to pig's diets, pigs LOST weight. Ironically, in attempting to meet the current orthodox demand for leaner meats, pigs may be finished with saturated fats (like beef tallow or coconut) instead of soybean oil. A recent study in Pig Progress , with authors sympathetic to the orthodox benefits of polyunsaturated fats, comparing the effects of sunflower oil diet to a beef tallow diet, did not report any changes in meat quality, but discovered a significant difference in adipose tissues reflecting the nature of the diets (with the beef tallow-diet animals higher in saturated and monounsaturated fats and lower in polyunsaturated fat) and the sunflower oil-diet pig fat with an unsatisfactorily high n-6 to n-3 PUFA ratio.
Similar concepts occur in other dietary decisions. For instance, grass-fed cows produce milk with a higher concentration of CLA, a "good" natural trans fat believed to help enhance insulin sensitivity, resist increases in belly fat, and raise good (HDL) cholesterol. Grass-fed meat producers claim a more ideal, natural Omega-6 to Omega-3 ratio. We also see that age (and the accumulative effects of nutritional choices over a lifetime) may be a factor in phenomena like atherosclerosis; Enig cites a number of studies showing comparable results across cultures with different diets. One reason I will eat sardines and younger tuna (cf. Wild Planet brand) or wild seafood (e.g., versus farm-raised salmon) deals with minimizing the risk of metabolized contaminants.
The Anomalous Studies Cited By Ms. Reinagel
The Danish study reported on macronutrient intakes and waist circumference. Waist circumference (> 35" for women, > 40" for men) is considered to be a high risk indicator for several conditions (e.g., diabetes, heart disease, etc.) The typical orthodox advice is to limit sources of saturated fat (including beef, eggs, dairy and red meat), substitute leaner meats (e.g., chicken), and replace them with polyunsaturated fats and carbohydrates. The study looked at results by gender along 21 food and beverage categories for a 5-year period of men and women (analyzed separately) between the ages of 50 and 64. What's particularly interesting is that for both genders, the consumption of red meat was inversely related to waist size, and for women, the consumption of dairy fats (e.g., butter, cheese, and cream) was also inversely related (whereas processed meats, poultry, and potatoes were directly related). Reinagel mentions, "Some would argue that a diet higher in fat and protein may be lower in carbohydrates and that carbohydrates drive insulin resistance and obesity." In particular, I would suggest (and I believe Enig would agree) that higher amounts of "bad" (high-glycemic) carbohydrates, n-6 PUFA's and trans fats are problematic, and minimally-processed whole foods (e.g., whole grain vs. white flour and unprocessed meats) are underrepresented. I would also add that the thermogenic nature of metabolizing protein and the satiety resulting from fats (including saturated fats) might help dieters limit their aggregate consumption of calories.
The second international study showed no relationship between certain identified foods (with saturated fats) (i.e., meat, eggs, dairy fats) and breast cancer.
Concluding Thoughts
I have not done empirical research in the nutrition sciences, but a number of studies I have seen seem to have issues with things like the use of self-report questionnaires, the nature of sampling (e.g., gender, age groups, etc.), the lack of standard measures/units, statistical power (e.g., small sample sizes), and single vs. multiple observation points. I'm also concerned with the liberal use of guidelines based not on confirmed hypothetical causal links, but motivated by correlational data. These guidelines are not often empirically verified. One classic example is the 8-glasses-of-water rule of thumb. When I attempted to debunk this myth in a low-carb forum a few years back, citing a prominent review on the topic by Heinz Valtin, I ran into a lot of resistance. (Subsequent reviews have repeated the same, and even snopes.com has addressed the issue.)
I am concerned about the amount of groupthink that Dr. Enig has encountered; she has been poking at some of the sacred cows in current medical practice and nutrition, such as putting otherwise healthy people on statin drugs based on arbitrary cholesterol levels. Many cultures (e.g., French, Eskimo and Asian), not to mention our own past, have eaten diets far richer in "banned" saturated fats without comparable CHD statistics. Whereas a more sedentary lifestyle has an obvious effect on a population where a majority of Americans are overweight, we still need to come to terms that the typical American diet today has a disproportionate amount of Omega-6's and trans fats, which are not well-metabolized by our bodies, and underconsumption of Omega-3's, not to mention a surplus of blood sugar-spiking refined or simple carbohydrates (e.g., sugar, breads, potatoes, etc.). We need to ask--if, holding cattle activity constant, cattle gain a lot of weight eating corn or soybeans but get thinner if you add coconut to their diet, do we have reason to believe that these foods are metabolized differently in humans? And if pigs finished on vegetable feed store a disproportionate amount of n-6 PUFA in their adipose issues, what are the implications for losing weight on an n-3 PUFA deficient diet?
Among other things, Enig has focused on dangerous trans fats (which have a double whammy of raising bad cholesterol and lowering good cholesterol); her dissertation suggested that trans fats impede the effectiveness of enzymes in dealing with carcinogens. [Trans fats are generated in the process of hydrogenating heat-unstable (primarily Omega-6) vegetable oils, which enables baking and improves food product shelf life; deep-frying with partially hydrogenated vegetable shortening, a staple for many fast-food restaurants, is another important dietary source.] She also cites a long list of studies of adverse affects related to vegetable oil consumption (for example, one 1994 study reported about three-quarters of an artery clog was unsaturated fats, and other studies mention adverse affects on mineral or Omega-3 metabolism).
One of the relevant points of discussion is the ratio of Omega-6 to Omega-3 polyunsaturated fats in the diet. Iin a more natural food setting, this is roughly 2:1; in a more contemporary diet, this ratio can range from nearly 10-20:1.
What comes to mind is the old adage: "you are what you eat". We see this clearly from examples in egg and meat production. Many "free-range" hens or hens fed (high Omega-3) flaxseed meal produce eggs higher in vitamin E and lower in calories and fats. In finishing animals (fattening them up for butchery), cattle have often been fed Omega-6 feed (e.g., corn and soybeans, which have certain thyroid-suppressing effects) Farmers also discovered when they added coconut to pig's diets, pigs LOST weight. Ironically, in attempting to meet the current orthodox demand for leaner meats, pigs may be finished with saturated fats (like beef tallow or coconut) instead of soybean oil. A recent study in Pig Progress , with authors sympathetic to the orthodox benefits of polyunsaturated fats, comparing the effects of sunflower oil diet to a beef tallow diet, did not report any changes in meat quality, but discovered a significant difference in adipose tissues reflecting the nature of the diets (with the beef tallow-diet animals higher in saturated and monounsaturated fats and lower in polyunsaturated fat) and the sunflower oil-diet pig fat with an unsatisfactorily high n-6 to n-3 PUFA ratio.
Similar concepts occur in other dietary decisions. For instance, grass-fed cows produce milk with a higher concentration of CLA, a "good" natural trans fat believed to help enhance insulin sensitivity, resist increases in belly fat, and raise good (HDL) cholesterol. Grass-fed meat producers claim a more ideal, natural Omega-6 to Omega-3 ratio. We also see that age (and the accumulative effects of nutritional choices over a lifetime) may be a factor in phenomena like atherosclerosis; Enig cites a number of studies showing comparable results across cultures with different diets. One reason I will eat sardines and younger tuna (cf. Wild Planet brand) or wild seafood (e.g., versus farm-raised salmon) deals with minimizing the risk of metabolized contaminants.
The Anomalous Studies Cited By Ms. Reinagel
The Danish study reported on macronutrient intakes and waist circumference. Waist circumference (> 35" for women, > 40" for men) is considered to be a high risk indicator for several conditions (e.g., diabetes, heart disease, etc.) The typical orthodox advice is to limit sources of saturated fat (including beef, eggs, dairy and red meat), substitute leaner meats (e.g., chicken), and replace them with polyunsaturated fats and carbohydrates. The study looked at results by gender along 21 food and beverage categories for a 5-year period of men and women (analyzed separately) between the ages of 50 and 64. What's particularly interesting is that for both genders, the consumption of red meat was inversely related to waist size, and for women, the consumption of dairy fats (e.g., butter, cheese, and cream) was also inversely related (whereas processed meats, poultry, and potatoes were directly related). Reinagel mentions, "Some would argue that a diet higher in fat and protein may be lower in carbohydrates and that carbohydrates drive insulin resistance and obesity." In particular, I would suggest (and I believe Enig would agree) that higher amounts of "bad" (high-glycemic) carbohydrates, n-6 PUFA's and trans fats are problematic, and minimally-processed whole foods (e.g., whole grain vs. white flour and unprocessed meats) are underrepresented. I would also add that the thermogenic nature of metabolizing protein and the satiety resulting from fats (including saturated fats) might help dieters limit their aggregate consumption of calories.
The second international study showed no relationship between certain identified foods (with saturated fats) (i.e., meat, eggs, dairy fats) and breast cancer.
Concluding Thoughts
I have not done empirical research in the nutrition sciences, but a number of studies I have seen seem to have issues with things like the use of self-report questionnaires, the nature of sampling (e.g., gender, age groups, etc.), the lack of standard measures/units, statistical power (e.g., small sample sizes), and single vs. multiple observation points. I'm also concerned with the liberal use of guidelines based not on confirmed hypothetical causal links, but motivated by correlational data. These guidelines are not often empirically verified. One classic example is the 8-glasses-of-water rule of thumb. When I attempted to debunk this myth in a low-carb forum a few years back, citing a prominent review on the topic by Heinz Valtin, I ran into a lot of resistance. (Subsequent reviews have repeated the same, and even snopes.com has addressed the issue.)
I am concerned about the amount of groupthink that Dr. Enig has encountered; she has been poking at some of the sacred cows in current medical practice and nutrition, such as putting otherwise healthy people on statin drugs based on arbitrary cholesterol levels. Many cultures (e.g., French, Eskimo and Asian), not to mention our own past, have eaten diets far richer in "banned" saturated fats without comparable CHD statistics. Whereas a more sedentary lifestyle has an obvious effect on a population where a majority of Americans are overweight, we still need to come to terms that the typical American diet today has a disproportionate amount of Omega-6's and trans fats, which are not well-metabolized by our bodies, and underconsumption of Omega-3's, not to mention a surplus of blood sugar-spiking refined or simple carbohydrates (e.g., sugar, breads, potatoes, etc.). We need to ask--if, holding cattle activity constant, cattle gain a lot of weight eating corn or soybeans but get thinner if you add coconut to their diet, do we have reason to believe that these foods are metabolized differently in humans? And if pigs finished on vegetable feed store a disproportionate amount of n-6 PUFA in their adipose issues, what are the implications for losing weight on an n-3 PUFA deficient diet?
I'm not optimistic about the future of useful nutrition research given the predominant Lipid Hypothesis paradigm (not unlike how politically-correct "global warming" groupthink stifles alternative points of view in the scientific community): you won't win grants to sponsor your research, you won't get published in highly visible journals or be hired by quality colleges or food companies, and there is no authentic scientific debate.
What about laymen, such as myself, knowing the scientific community seems unlikely to provide reliable, useful, consistent results in the near future? I think one thing, from my own experience with the development and validation of measures, is that laymen need to express some skepticism about artificial dietary benchmarks--e.g., limit saturated fat to under 10%, limit carbohydrates to under 20 grams daily, etc. Second, consider a variety of foods in one's diet, because meats, vegetables, nuts, etc., can vary in nutrition (e.g., various vitamins and minerals).
Third, be wary of food processing or filtering. Take, for instance, the almost slavish preference for poultry white meat (mostly because of its low-fat nature); dark meat, on the other hand, has almost twice the amount of iron and zinc, key elements of a healthy diet. Another prominent example is vilification of egg yolks (at the expense of egg whites): one estimate is about 90% of the nutrients in an egg are in the yolk. So when people start filtering out nutritious animal parts, cream from milk or elements of an egg or grains (to make white flour) to be consistent with arbitrary dietary restrictions, I believe they need to stop and think: What is the function of these filtered elements? For example, does the yolk provide any useful purpose to a hatching chick? Does dairy cream provide any value for the weaning calf? And if it is nutritionally valuable to a young animal, why would it not be nutritionally valuable to us? The issue, in my view, is not removing these nutritional elements but in enjoying them in moderation.
Finally, keep your diet in aggregate nutritional balance. For instance, I think many (if not most) Americans do not get enough Omega-3's and soluble fiber in their diets. To bring one's n-6/n-3 PUFA ratio in balance, you should decrease the n-6 PUFA's and/or raise the n-3 PUFA's in your diet--and consider eating products where source feed reflects a better nutritional balance (e.g., grass-fed animals).
