High Carb vs Low Carb? I'm Confused. - 3/18/2010
Dr. Karl Nadolsky
The views expressed in this article are those of the author(s) and do not necessarily reflect the official policy or position of the Department of the Navy, Department of Defense, or the United States Government.
There are so many opinions that have been publicized in recent years as to what macronutrients people should be eating for weight loss and health that the majority of those who want the truth, including physicians, are either really confused or are hung up on recommendations which are based upon myth, hear-say, folk-lore, and unfortunately unfounded information. That is why we want to promote diet in terms of actual scientific and physiologic mechanisms backed by evidence-based medicine. We built our philosophy and food pyramid using the most recent and up to date physiologic knowledge and research so that physicians and their patients can have a reliable source to learn about nutrition. Here I will present a few studies to help with the understanding of the methods behind our madness and to give guidance for the conundrum of carbohydrate, fat, and protein intake.
Low carbohydrate vs. high carbohydrate diets for weight loss and internal health have been discussed at the water-cooler for the past decade or more. If you have read about our food pyramid and what we consider quality carbohydrate consumption, it is not necessarily of our utmost concern the actual amount of carbohydrates that you eat because if the content is mostly made up of vegetables, some fruit, and a bit of high fiber (“low carb”) starch product, you will be eating mostly fiber and precious nutrients which are far from empty calories in addition to providing a low glycemic load/index. Those foods will lead to weight loss and will not cause immediate intravascular inflammation leading to blood vessel disease at the time of consumption. But I know that that is not what the question is, so here’s the evidence: One recent study1 compared a bunch of obese individuals randomized to either a “high carb, low protein” diet (>220g carbs daily and 0.8g/kg body weight protein daily) or a “low carb, moderate protein” diet (<170g carbs daily and 1.6g/kg protein daily). Both diets were calorically restricted by 500 calories daily to promote weight loss, but the “low carb, mod protein” dieters actually had greater improvements in their body composition, cholesterol profile, and intravascular effects right after eating. Another im
portant study2 showed that low carbohydrate diets resulted in quicker weight loss than low fat diets for obese individuals, but more importantly those people with low carbohydrated diets continued to improve on the inside based upon their favorable cholesterol changes and glycemic control (hemoglobin A1c). Along those same lines, the New England Journal of Medicine published a study3 comparing low carbohydrate (without calorie restriction), Mediterranean (quality fats with calorie restriction), and low fat (with calorie restriction) diets among middle-aged (app. 52 yrs old), mildly obese (BMI 31) patients. There was weight loss with all groups, but was greatest in the low-carb and Mediterranean diets while LDL (bad cholesterol) had the greatest improvement in the Mediterranean dieters and HDL (good cholesterol) increased most with the low-carb folks. The New England Journal of Medicine followed that up by publishing a very large study4 which went ahead and confirmed what we have known for a long time, that calories still count. The study compared different ratios of macronutrients in diets without specifying the sources or types of carbohydrates, fats, or proteins. The results showed that it did not matter whether it was low carb, low fat, or low protein, as long as it was low calorie, weight was lost. Of course without investigating the types of fat, carbohydrate, or protein it really didn’t give much more specific information like the other more specific studies that we are discussing. Yet another study5 
recently published in the Nutrition and Metabolism journal split hairs further by comparing a low carbohydrate, ketogenic diet (<20g carbohydrate daily) vs a low glycemic diet, reduced calorie diet (500kcal below personal maintenance) randomly administered to 84 obese diabetic patients along with counseling and exercise recommendations with analysis of hemoglobin A1c. The average difference in HbA1c was -1.5% vs -0.5% favoring the low-carbohydrate, ketogenic diet plus greater improvements in weight loss (-11.1 lbs vs. -6.9 lbs) and HDL (+5.6 vs. 0). 95% of the participants who finished the study in the ketogenic arm also reduced or eliminated the necessity for their oral diabetic medications.
Many people have caught on that quality sources of protein are very important for health, body composition, and mental well-being but there is still some resistance in society to moderate or high protein diets. We base a lot of our philosophical ideas on the fact that primitive humans were hunter-gatherers who ate an abundance of lean meat and vegetables. They did not have the obesity, diabetes, or cardiovascular disease that we have today. The research shows that good sources of protein eaten throughout the day tend to be optimal for many physiologic reasons. Certain people with specific kidney problems or other medical problems may need to limit their protein intake to a minimum and everyone needs to consult their physicians before making adjustments to their diets. Most people do not need excessive amounts of protein unless they are sick or are involved in highly intense athletic training where large intakes of protein are needed to recover. Studies6 have shown us that eating protein with every meal blunts some of the adverse effects of carbohydrates, improves glycemic control, and leads to better compositions from fat loss and muscle maintenance.
The take home point from all of the studies which have been done is that an optimal diet consists of a carbohydrate load that is small but also high in quality nutrients and fiber. Vegetables, fruit, and high fiber:carbohydrate ratio starches do not cause immediate detrimental cardiovascular changes right after eating and lead to long term fat loss and favorable cholesterol/anti-atherogenic profiles. Fat intake should be moderate and balanced among quality sources to include a plethora of mono-unsaturated oils (olive oil and almonds), omega-6 polyunsaturated oils (nuts), omega-3 polyunsaturated oils (salmon and flax), and a little bit of saturated fat (free-range chicken eggs, coconut, lean meats). For greater detail and understanding of how to include quality fats in a healthful diet see our article on “Balancing Act: Fat Intake” Protein consumption is ideally from lean animals and their milk or dairy products which are also lean and should be included in every meal for a balanced post-prandial influence on your body. (editor's note: Using Glycosolve with berberine along with a Leaner Living diet will enhance blood sugar regulation and improve lipid metabolism)
1. Walker et al. Moderate carbohydrate, moderate protein weight loss diet reduces cardiovascular disease risk compared to high carbohydrate, low protein diet in obese adults: A randomized clinical trial Nutrition & Metabolism 2008, 5:30 doi:10.1186/1743-7075-5-30 A weight loss diet with moderate carbohydrate, moderate protein results in more favorable changes in body composition, dyslipidemia, and post-prandial INS response compared to a high carbohydrate, low protein diet suggesting an additional benefit beyond weight management to include augmented risk reduction for metabolic disease. This study was a parallel-arm randomized 4 mo weight loss trial. Adults matched on BMI (33.6) consumed energy restricted diets (deficit ~ 500kcal/d): PRO (1.6 g.kg-1.d-1 protein and < 170g/d carbohydrate) or CHO (0.8 g.kg-1.d-1 protein and > 220 g/d carbohydrate) for 4 mos. Meal challenges of respective diets were utilized for determination of blood lipids and post-prandial INS and glucose response at the beginning and end of the study.
2. Clin Pract Endocrinol Metab 4(3):, 2008. Results from multiple large studies have shown that the low-carbohydrate dieters lost significantly more weight than comparable participants following a low-fat diet. Additional benefits of the low-carbohydrate diet suggested by these studies included greater improvement in levels of triglycerides[21,22] and HDL-cholesterol.[22] In addition, diabetic participants in the low-carbohydrate diet group showed a greater reduction in serum glucose levels than those in the low-fat diet group. Insulin sensitivity, measured only in participants without diabetes, improved more among those on the low-carbohydrate diet. Foster and colleagues studied the impact of 1 year of dieting in obese men and women and found that the low-carbohydrate diet was more effective for weight loss after 3 and 6 months than the low-fat diet but, importantly, not after 12 months;[23] however, the low-carbohydrate group continued to exhibit greater improvement in specific cardiovascular risk factors at 12 months (i.e. increased HDL-cholesterol and decreased triglyceride levels). These findings were supported by a 1-year follow-up of participants from a 6-month RCT,[24] which additionally showed that, for diabetic participants, HbA1c levels decreased more in the low-carbohydrate group. Several other controlled studies of carbohydrate-restricted diets with long-term follow-up have shown similar results, with no differential in weight loss between the diet groups beyond 6 months, but continued improvement in HDL-cholesterol and triglyceride levels in low-carbohydrate groups. - Nat Clin Pract Endocrinol Metab 4(3):, 2008.
3. Shai et al. Both a low-carbohydrate diet or a Mediterranean-style diet out-perform low-fat diets with more favorable effects on lipids and/or glycemic control. N Engl J Med 359:229, July 17, 2008 A two-year study, which managed to keep almost 85% of the 322 study participants on one of the three diets for the entire period, offers the hope that weight-loss diets can be tailored to personal preferences, without sacrificing efficacy, researchers say. At the start of the study, DIRECT subjects were middle-aged (mean age 52 years) and mildly obese (body-mass index = 31). All participants were randomized to one of three diets: low-fat/restricted-calorie diet; Mediterranean/restricted-calorie diet; or low-carbohydrate diet, with no restriction on calories. Weight loss occurred in all three groups over the 24 months but was greater in the Mediterranean and low-carb groups. Changes in lipid parameters were also most striking in the low-carb and Mediterranean-diet groups. High-density lipoprotein (HDL) increases and triglyceride decreases were most pronounced in the low-carb group, while reductions in low-density lipoprotein (LDL) cholesterol were greatest in the Mediterranean-diet group. Reductions in total cholesterol/HDL ratio were greatest in the low-carb group, closely followed by the Mediterranean-diet group. In the subset of patients with diabetes the Mediterranean diet appeared to improve fasting plasma glucose levels. - Shai and colleagues publish the results of the Dietary Intervention Randomized Controlled Trial (DIRECT) in the July 17, 2008 issue of the New England Journal of Medicine.
4. Sacks et al. Comparison of Weight-Loss Diets with Different Compositions of Fat, Protein, and Carbohydrates. N Engl J Med 360:859, February 26, 2009 Background The possible advantage for weight loss of a diet that emphasizes protein, fat, or carbohydrates has not been established, and there are few studies that extend beyond 1 year. Methods We randomly assigned 811 overweight adults to one of four diets; the targeted percentages of energy derived from fat, protein, and carbohydrates in the four diets were 20, 15, and 65%; 20, 25, and 55%; 40, 15, and 45%; and 40, 25, and 35%. The diets consisted of similar foods and met guidelines for cardiovascular health. The participants were offered group and individual instructional sessions for 2 years. The primary outcome was the change in body weight after 2 years in two-by-two factorial comparisons of low fat versus high fat and average protein versus high protein and in the comparison of highest and lowest carbohydrate content. Results At 6 months, participants assigned to each diet had lost an average of 6 kg, which represented 7% of their initial weight; they began to regain weight after 12 months. By 2 years, weight loss remained similar in those who were assigned to a diet with 15% protein and those assigned to a diet with 25% protein (3.0 and 3.6 kg, respectively); in those assigned to a diet with 20% fat and those assigned to a diet with 40% fat (3.3 kg for both groups); and in those assigned to a diet with 65% carbohydrates and those assigned to a diet with 35% carbohydrates (2.9 and 3.4 kg, respectively) (P>0.20 for all comparisons). Among the 80% of participants who completed the trial, the average weight loss was 4 kg; 14 to 15% of the participants had a reduction of at least 10% of their initial body weight. Satiety, hunger, satisfaction with the diet, and attendance at group sessions were similar for all diets; attendance was strongly associated with weight loss (0.2 kg per session attended). The diets improved lipid-related risk factors and fasting insulin levels. Conclusions Reduced-calorie diets result in clinically meaningful weight loss regardless of which macronutrients they emphasize.
5. Westman et al. The effect of a low-carbohydrate, ketogenic diet versus a low-glycemic index diet on glycemic control in type 2 diabetes mellitus. Nutrition & Metabolism 2008; 19 Dec
6. Björck I. Metabolic effects of amino acid mixtures and whey protein in healthy subjects: studies using glucose-equivalent drinks. Am J Clin Nutr 2007;85:996 –1004. McFarlane S. The case for low carbohydrate diets in diabetes management. Nutr Metab 2005;2:16 –24. Lean protein of high biological value (not the favored protein sources in the modern U.S. diet, such as regular ground beef from non-grazing cows, sausage, bacon, and cheese, are excessively high in both calories and saturated fats and tend to worsen post-prandial dysmetabolism.)will both reduce post-meal glucose excursion and improve satiety. In a study of healthy individuals, the addition of whey protein to a pure glucose drink lowered the post-prandial blood glucose area under the curve by 56%, and increased the insulin response by 60%. dietary protein has a thermogenic effect whereby it increases the basal metabolic rate, which is not the case with ingested carbohydrates. Thus, protein of high biological quality such as egg whites, fish, game meat (and other very lean red meats), skinless poultry breast meat, and whey protein (or other nonfat dairy protein) when eaten with meals will dampen down post-prandial inflammation and can help prevent obesity according to studies.
