The NESS » The Skeptic’s Diet. January 2. 00. 5 (updated August 2. Steven Novella, MDAn obese friend of mine commented on how well his new diet was going, as he absentmindedly devoured an entire low- carb cheesecake while happily engaged in his sedentary pastime. The correct information is mixed in there too, if you know where to look and how to recognize it when you see it, but sadly, for the average person, it is lost in the noise. You have probably heard the statistics before, as they have become the standard preface to any article or tome on diet and weight loss. America is fat. The 2. CDC) indicate that in 2. BMI of 3. 0 or greater) was 2. Mokdad 2. 00. 3). The numbers for 2. Flegal 2. 01. 0). The most recent data does indicate, however, that the trend is leveling off in the last decade. The National Center for Health Statistics estimates that 6. United States are overweight (BMI of 2. Children and adolescents are increasingly overweight as well, and the degree to which Americans are overweight is increasing. The prevalence of obesity is about the same across age, sex, race, and level of education, although it tends to be higher at lower socioeconomic levels. The estimated direct annual healthcare costs of obesity is $9. There’s plenty of blame to go around for what is being called the 2. The western lifestyle is always the first target of blame, for good reason. Americans eat too much and exercise too little. We have an increasingly sedentary lifestyle, with desk- jobs and video games taking up an increasing portion of our time, displacing manual labor and sporting activity. The American diet also tends to be dense in calories and large in portion. A recent CDC report indicates that Americans are eating more. Between 1. 97. 1 and 2. American’s daily calorie intake increased by 1. CDC 2. 00. 4). The same report also indicates that the portion of calories from carbohydrates increased during the same period, while fat intake increased slightly and protein intake decreased slightly. The additional calories in the American diet was largely from increased carbohydrates. While increased calorie intake is certainly to blame, I place a significant portion of the blame for America’s dieting woes on nutritional nonsense itself. Fad diets and misinformation give people false hope, failed strategies, and distract them from the real causes of their obesity, and the real solutions. Mercola's Nutrition Plan will give you tips on healthy eating and exercise, as well as other lifestyle strategies to help you achieve optimal health. Read our independent reviews of the top online diet programs to find the best one to help you work toward your weight-loss goals. Fad Diets. Charlatans will happily flock to any realm where there is a significant gap between the public’s desires and their knowledge. In the area of dieting, there is a vibrant industry of weight- loss gurus and fad diets, in a seemingly never- ending cycle. A casual perusal of any large bookstore chain’s shelves will reveal dozens of popular titles. Most readers will recognize the Atkin’s diet, now enjoying the top spot in popularity, but many others are still popular, such as the South Beach diet, the Pritikin diet, and the Zone. Fad diets, as a common theme, usually focus on the proportion of various macronutrients in one’s diet. Calories (in physics, the basic unit of energy is the calorie, but in nutrition a thousand such calories, or a kilocalorie, is also referred to as a Calorie, sometimes distinguished with a big “C”) in our diet come from either protein, fat, or carbohydrates – the macronutrients. Alcohol also contains calories, but otherwise there is no other source of energy in our diet. The basis of most fad diets is to claim that weight loss (and other health benefits) can be achieved by altering one’s diet so that it contains an optimal proportion of the macronutrients. This usually takes the form of labeling one of the macronutrients as “bad” and minimizing it in the diet. In the 1. 97. 0’s and 8.
In the 1. 99. 0’s and the new century carbohydrates have clearly displaced fat as the bad boy on the block, and a low- carb craze is in full swing. Enter the Zone, although in the low- carb camp, went one step further to claim that there was a magical zone of proportions of the three macronutrients which would produce optimal health and weight loss. The problem will all of the popular diets is that they followed the short and quick path to popular appeal and bypassed the more arduous path of scientific validity. In short, the proponents of such diets never did valid research to establish their premises or their clinical claims. Meanwhile, legitimate researchers have been slowly and quietly advancing our knowledge of nutrition and weight loss, but their findings have been largely disconnected from the cycle of popular marketing and belief. Occasionally, a guru will cherry- pick a study or two which appears to support their position, but largely only useless anecdotes and hand- waving explanations are offered to support claims. Low- Carb Diets. You can’t go to a food store or restaurant these days without being inundated with low- carb, or Atkins- friendly, options. Atkins has been making his low- carb claims since the 1. In the 1. 99. 0’s, however, other dieting gurus, like Spears of Enter the Zone fame, started pushing the low- carb claims, and the momentum has clearly shifted. Interestingly, despite decades of time and millions of books sold, Atkins claimed rather lamely that he did not have the resources to do proper clinical studies of his claims. The low- carb diet philosophy has several key components. One claim that may have some legitimacy is that carbohydrates stimulate the release of insulin, which then drives down the blood sugar level, which in turn may drive rebound hunger causing further calorie intake. So far the studies have shown that low carbohydrate diets may reduce hunger and lead to decreased caloric intake, but they also show that any such advantage only lasts for 6- 1. Nordmann 2. 00. 6). Long term, there does not appear to be any advantage to low- carb diets. Perhaps our bodies adjust to our new diets and we reach a new equilibrium in terms of hunger. Regardless, it is important to note that there does not appear to be any long term advantage to decreased carbohydrates. It is also important to point out that in clinical trials comparing various diets in obese subjects, overall weight loss is modest, and subjects are usually gaining weight back by the end of the study. In the review cited above, for example, at 6 months subjects on a low carb diet lost on average 3. By 1. 2, months, however, the difference was only 1. And – on average subjects were gaining weight toward the end of the study, with total weight loss being negligible. The South Beach diet focuses on glycemic index rather than total carbohydrates, and this does make more sense, although supportive data is still lacking. Glycemic index refers to the rapidity with which a carbohydrate is broken down into glucose, the form of sugar that is used by cells to make energy and which stimulates insulin release. Most people are surprised to learn that potatoes, which are high in starch (starch is basically a long chain of glucose molecules strung together), is metabolized into glucose more quickly than table sugar (which is sucrose and needs to be broken down into glucose and fructose). Therefore, it may be more important to focus on the kinds of carbohydrates we eat rather than on the total amount. Nutritionists now do recommend substituting whole grains for processed white bread, brown rice for white, whole- wheat pasta for white, and avoiding too much sugar. It is not clear if this aids in weight loss, but there may be other health benefits, for example avoiding diabetes (more on this below). However, most of the fad diets either strongly suggest or directly claim that you can lose weight without reducing calories simply by avoiding carbohydrate calories. This is where the fad diets clearly depart from the scientific evidence, which overwhelmingly supports the idea that a calorie is a calorie. People lose weight because they burn more calories than they consume, and all weight loss diets work by reducing calories. Another aspect of the low- carb diets worth commenting on is the phenomenon known as ketosis. Although our bodies can burn fat and protein for energy, glucose is the primary fuel of cells. Our brains are especially dependent upon a steady supply of glucose for energy, and this is why we need to maintain a certain blood glucose level for optimal health. We cannot convert fat or protein into glucose, and therefore must consume a certain amount of carbohydrates in order to meet the body’s needs. If the cells in our body are starved of carbohydrates then they produce proteins known as ketones and burn the ketones as an emergency substitute for glucose. This leads to a build up of ketones in the blood, a metabolic state known as ketosis. Diabetics can go into ketosis, not because they are starved of glucose but because of insulin dysfunction, preventing adequate transport of glucose from the blood into cells. So even though there is plenty of glucose around, the cells can’t get access to it and must rely upon ketones for quick energy. Another way to achieve ketosis, however, is to simply deprive the body of carbohydrates. The Atkins diet recommends decreasing carbohydrate intake to less than 2. Some more extreme low- carb diets call for total carbohydrate intake of 5% or less. Ketosis is generally considered to be an unhealthy metabolic state. Ketones are acidic, and high levels of ketones in the blood therefore lead to another metabolic state known as acidosis. One side effect of ketoacidosis is a decrease in hunger, and that is likely a major contributor to the apparent short- term weight loss that low- carb dieters experience. Again, I will emphasize that long term health and weight control cannot be achieved through short- term strategies that result in unhealthy metabolic states. Low- Fat Diets. Just like with carbs, you can’t lose weight by reducing fat unless you also reduce total caloric intake. Glycemic index diet: What's behind the claims. Diet details. A GI diet prescribes meals primarily of foods that have low values. Examples of foods with low, middle and high GI values include the following: Low GI: Green vegetables, most fruits, raw carrots, kidney beans, chickpeas, lentils and bran breakfast cereals. Medium GI: Sweet corn, bananas, raw pineapple, raisins, oat breakfast cereals, and multigrain, oat bran or rye bread. High: White rice, white bread and potatoes. Commercial GI diets may describe foods as having slow carbs or fast carbs. In general, foods with a low GI value are digested and absorbed relatively slowly, and those with high values are absorbed quickly. Commercial GI diets have varying recommendations for portion size, as well as protein and fat consumption. Results. Studies of the benefits of GI diets have produced mixed results. Weight loss. In a 2. GI or low- GL diets, researchers concluded that the diets were . Ten studies showed a slight improvement — but not a statistically significant improvement — in weight loss. In another 2. 01. American Diabetes Association and the European Association for the Study of Diabetes. The results showed that low- carbohydrate diets and Mediterranean diets provided more weight- loss benefit than low- GI diets. During the six months following this weight loss, people who ate a low- GI, high- protein diet were more likely to stick with their diet plan and not regain the weight they had lost. Blood glucose control. A treatment goal for people with diabetes is to keep after- eating and average blood glucose levels as close to nondiabetic levels as possible. This tight control helps prevent or slow the development of complications associated with the disease. Some clinical studies have shown that a low- GI diet may help people with diabetes control blood glucose levels, although the observed effects may also be attributed to low- calorie, high- fiber content of the diets prescribed in the study. Cholesterol. Reviews of trials measuring the impact of low- GI index diets on cholesterol have shown fairly consistent evidence that such diets may help lower total cholesterol, as well as low- density lipoproteins (the . The thinking is that high- GI food causes a rapid increase in blood glucose, a rapid insulin response and a subsequent rapid return to feeling hungry. Low- GI foods would, in turn, delay feelings of hunger. Clinical investigations of this theory have produced mixed results. Also, if a low- GI diet suppresses appetite, the long- term effect should be that such a diet would result over the long term in people choosing to eat less and better manage their weight. The long- term clinical research does not, however, demonstrate this effect. The bottom line. In order for you to maintain your current weight, you need to burn as many calories as you consume. To lose weight, you need to burn more calories than you consume. Weight loss is best done with a combination of reducing calories in your diet and increasing your physical activity and exercise. Selecting foods based on a glycemic index or glycemic load value may help you manage your weight because many foods that should be included in a well- balanced, low- fat, healthy diet with minimally processed foods — whole- grain products, fruits, vegetables and low- fat dairy products — have low GI values. For some people, a commercial low- GI diet may provide needed direction to help them make better choices for a healthy diet plan. The researchers who maintain the GI database caution, however, that the . Overweight and obesity. Nutrition Care Manual. Academy of Nutrition and Dietetics. Accessed June 2, 2. Ajala O, et al. Systematic review and meta- analysis of different dietary approaches to the management of type 2 diabetes. American Journal of Clinical Nutrition. Esfahani A, et al. The application of the glycemic index and glycemic load in weight loss: A review of the clinical evidence. Livesey G, et al. Glycemic response and health — A systematic review and meta- analysis: Relations between dietary glycemic properties and health outcomes. American Journal of Clinical Nutrition. S. Kristo AS, et al. Effect of diets differing in glycemic index and glycemic load on cardiovascular risk factors: Review of randomized controlled- feeding trials. Hensrud DD (expert opinion). Mayo Clinic, Rochester, Minn. June 3. 0, 2. 01. Venn BJ, et al. Glycemic index and glycemic load: Measurement issues and their effect on diet- disease relationships. European Journal of Clinical Nutrition. Suppl 1: S1. 22. Simin L, et al. Dietary carbohydrates. Accessed May 3. 0, 2. Atkinson FS, et al. International tables of glycemic index and glycemic load values: 2. Diabetes Care. 2. Glycemic index and diabetes. American Diabetes Association. Accessed May 3. 0, 2. Bornet FR, et al. Glycaemic response to foods: Impact on satiety and long- term weight regulation. Tight diabetes control. American Diabetes Association. Accessed June 1. 0, 2. Fleming P, et al. Low- glycaemic index diets in the management of blood lipids: A systematic review and meta- analysis. Family Practice. 2. Goff LM, et al. Low glycaemic index diets and blood lipids: A systematic review and meta- analysis of randomised controlled trials. Nutrition, Metabolism and Cardiovascular Diseases. Karl JP, et al. Effect of glycemic load on eating behavior self- efficacy during weight loss. C: 2. 04. Dietary guidelines for Americans, 2. Department of Health and Human Services. Accessed May 3. 0, 2. See more In- depth.
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