Low Carbohydrate (CHO) Diet Summaries



Produce for Better Health Foundation

Low-Carbohydrate Diet

Talking Points

• There is an overwhelming body of scientific evidence in support of the relationship between fruit and vegetable intake and health

• At present, there is no published scientific evidence that low- carbohydrate diets are more effective in producing long-term weight loss than adopting healthy eating habits and regular physical activity

• Low-carbohydrate diets—to the extent that they restrict fruit and vegetable intake—are unhealthy and inhibit intake of important nutrients, fiber and phytochemicals**

• Including 5 to 9 servings of nutrient-dense, colorful fruits and vegetables in an overall diet which is low in saturated and trans fat, and encourages whole grain intake, is the proper foundation upon which to build and maintain health

• **Phytochemicals are often referred to as phytonutrients

Produce for Better Health Foundation

Backgrounder—Low-Carbohydrate Diets

October 2003

Low-carbohydrate diets—to the degree that they restrict fruit and vegetable intake—are unhealthy and inhibit intake of important health-promoting nutrients, fiber and phytochemicals. In the constant quest for weight loss, Americans have lately turned more toward low-carbohydrate diets. At present, there is no published scientific evidence that these diets are more effective in producing long-term weight loss than adopting healthy eating habits. There is, however, an overwhelming body of scientific evidence in support of the relationship between fruit and vegetable intake and health. With science touting the emerging health benefits associated with phytochemicals, and with the numbers of overweight/obese children and adults growing at an alarming rate, it is important now, more than ever, to embrace healthful eating accompanied by appropriate physical activity. Including 5 to 9 servings of nutrient-dense, colorful fruits and vegetables in an overall diet which is low in saturated and trans fat, and encourages whole grain intake, is the proper foundation upon which to build and maintain health. (1)

Rationale

Obesity is a glaring public health issue in our country today. According to the Centers for Disease Control and Prevention (CDC), approximately 64% of Americans are now officially classified as overweight or obese, and the trend is moving upward. (2) In addition, the statistics for childhood overweight have increased from 11% to 15% in the years between the National Health and Nutrition Examination Survey (NHANES) III (1988-94), and the 1999-2000 NHANES. (2)

This is a nation where less than 20% of individuals consume a minimum of 5 servings of fruits and vegetables per day. (3) Because of this, the vast majority of Americans miss the benefits that fruits and vegetables provide in helping to maintain a healthy weight and reducing the risk of diabetes, heart disease, high blood pressure, and several types of cancer. While Americans might not focus on their risk for chronic disease, they are very aware of their perceived body image. So much so, that they are drawn to a quick fix in order to lose weight. This is evident based on the strong renewed interest in the low-carbohydrate diets of the 70’s, which have been on the best seller list for many years.

When evaluating some of the most popular low-carbohydrate diets on the market, a common thread emerges: the insulin-obesity connection. Insulin is a hormone that allows for the uptake of glucose (digested carbohydrate) into the cells for energy. Proponents of these diets suggest a connection between high-circulating levels of insulin in the blood and the “unavoidable” storage of glucose as fat in the body. Because glucose is the result of carbohydrate metabolism, these diets label all or many carbohydrates as “bad” and discourage their consumption. In fact, low-carbohydrate diets restrict or eliminate foods such as fruits and vegetables, and many then encourage the use of supplements. However, supplements do not provide the synergistic benefits of whole foods. There is a growing body of evidence that supports the fact that nutrients and other food compounds, when working together, provide for a greater health benefit than they would individually as a supplement. (4) By denouncing carbohydrate in general, without respect to fruits, vegetables and whole grains, a huge disservice is done to the consumer, and their health can be negatively affected because of it. In contrast to the low-carbohydrate diet theory, there is ample evidence of the health benefits of diets rich in fruits, vegetables and whole grains, and low in saturated and trans fat. (5-7)

There is a need to differentiate between refined carbohydrates and fiber-containing, nutrient-dense, low-calorie fruits, vegetables and whole grains. Many low-carbohydrate diets restrict or eliminate fruits and vegetables based on the concept of “glycemic index.” The glycemic index (GI) is a number that identifies how quickly a specific amount of carbohydrate from a food will affect blood sugar levels. Theoretically, the higher the number, the faster it will cause a spike in the blood sugar, necessitating an insulin response. One problem with GI is that foods aren’t always eaten individually. When foods are eaten together as a meal, the GI is reflective of the components of that meal.

Most fruits and vegetables have a low GI; however, some end up on lists of “foods to avoid” because their GI is considered too high. To keep this in perspective, it is important to know that in general, all fruits and vegetables have a low glycemic load, which is defined as GI multiplied by carbohydrate content. (8) This means that fruits and vegetables do not contain much CHO and therefore are unlikely to adversely impact blood sugar management. Fruits and vegetables as snacks are nutrient-packed and contain fiber and phytochemicals that are of great benefit in an overall healthy diet.

The American Diabetes Association, citing insufficient scientific evidence, does not endorse the use of GI in choosing foods to control blood sugar. (9) Many health professionals also dispute GI and the insulin-obesity connection, and rather support the theory of energy balance. Simply put, you will gain weight if you take in more calories than you expend. Substituting fruits and vegetables for high calorie foods is a great way to reduce calorie intake without feeling deprived.

With overweight and obesity as strong risk factors for many chronic diseases, it is evident that Americans are in the middle of a health crisis. The cost of treating obesity in the year 2000 was an astronomical $117 billion. (2) With solid scientific evidence supporting the benefits of fruit and vegetable intake in maintaining health and preventing many chronic diseases, and the burgeoning role that their phytochemicals play in that regard, the elimination of appropriately prepared fruits or vegetables from the American diet has the potential to adversely affect health.

On-going Research

It is acknowledged that new studies on this timely subject will likely abound. The Produce for Better Health Foundation will keep abreast of all research in this area and, will update this backgrounder as deemed appropriate in an effort to keep the industry we serve adequately informed.

Low Carbohydrate (CHO) Diet Summaries

Dr. Atkins’ New Diet Revolution (10)

• Premise based on the belief that increased carbohydrate intake causes an overproduction of the hormone insulin, which leads to hunger and weight gain

• Allows unrestricted amounts of protein and fats, but severely limits carbohydrates such as pasta, breads and fruits

• Diet plan consists of four phases:

1. Induction—designed to “get your weight loss program off to a fast start.” Limits CHO intake to just 20 grams (g) of “Net Carbs” (total CHO content of a food less the fiber content) a day for a minimum of two weeks.

2. Ongoing Weight Loss—start allowing certain “nutrient rich” CHO back into diet; add 5g Net Carbs per day in weekly increments until weight loss stops. At this point, drop back 5g and this is the number of Net Carbs you can have and still lose weight. This phase is continued until within 5-10 pounds of desired goal weight.

3. Pre-Maintenance—continue slow weight loss by increasing daily carbohydrate intake by no more than 10g Net Carbs each week—as long as you are still losing weight. Continue until you reach goal weight.

4. Lifetime Maintenance—maintaining goal weight by adhering to your Atkins Carbohydrate Equilibrium (ACE) number. This individualized number is the amount of Net Carbs you can eat without gaining or losing weight (usually between 45-100g/day for most people on the program).

• Restriction of CHO in the diet causes the body to go into ketosis, which enables fat stores-as opposed to CHO-to be used for energy.

• In the 2003 book Atkins for Life there is a greater emphasis placed on eating vegetables and fruits in the last three phases of the diet. Fruits and vegetables are divided into three groups based on Atkins Glycemic Ranking. This relegates many fruits and vegetables to the “eat in moderation” or “eat sparingly” categories.

The Carbohydrate Addict’s Diet (11)

• Premise based on the idea that a “carbohydrate addict” continually produces high levels of insulin in the body due to the frequency of CHO-rich foods eaten, resulting in more carbohydrate cravings. Frequency and duration of CHO intake negatively affects the addict.

• Consists of two Complementary Meals (high-fiber, low-fat & low-carb) and one Reward Meal per day. It is during the Reward meal (balanced 1/3 protein, 1/3 low-carb vegetables, and 1/3 high-carb foods) that all desired CHO-rich foods must be eaten. There is no limit on quantity, but duration is limited to 60 minutes (consecutively, at one sitting).

• All fruits, fruit juices, and many vegetables are restricted throughout the day, and only allowed during the Reward meal.

• Has no induction or maintenance phase. Five different plans exist and will change weekly depending on how much weight was lost that week, and how much weight the dieter wants to lose for the next week.

Sugar Busters! (12)

• Premise based on the belief that refined carbohydrates cause obesity by raising blood sugar.

• Authors do not consider it a “low-carbohydrate diet,” but rather a “correct carbohydrate lifestyle.” (Allows ~40% of calories from carbohydrate along with 30% protein and 30% fat).

• Rates acceptability of foods based on their glycemic index (GI), which is used to modulate the body’s insulin secretion.

• Advocates eliminating refined sugar, and eating whole-grain unrefined foods (basically high fiber and low GI diet).

• Allows most fruits and vegetables except those with a high GI (i.e., potatoes, beets, carrots, other starchy root vegetables).

South Beach Diet (13)

• Premise based on the belief that much of our excess weight comes from the type of carbohydrates that we eat. Born from the disillusionment of the low-fat, high-carb recommendations, which “have only gotten Americans fatter.”

• Atkins-like diet, but advocates mono/poly unsaturated fats (“good fats”) and whole grains, vegetables and fruits (“good carbs”).

• Three phases, with Phase 1 severely limiting carbohydrates for 14 days. This phase attempts to “begin reversing the body’s likely inability to process sugars and starches properly.” Phase 2 re-introduces “good carbs” like fruits and whole grains while still allowing for weight loss. Fruits with a high glycemic index are added back into the diet slowly (e.g., bananas, pineapple, mango, and others).

The Zone (14)

• Premise based on the belief that a specific balance of carbohydrate, protein and fat must be attained at each meal in order to achieve “hormonal control” over insulin and glucagons (releases stored glucose back into the blood). “Excess insulin makes you fat and keeps you fat.”

• “The Zone” refers to the range in which to keep insulin levels.

• Severe calorie restriction; restricts refined carbohydrates.

• Does advocate liberal fruit and vegetable intake; however, emphasizes the need to be selective. Labels many fruits and starchy vegetables as “Zone-hostile.”

• Many rules regarding meal composition and meal timing to stay in “the Zone.”

Other books on the market don’t necessarily label themselves as a “low-carbohydrate diet,” but they do advocate eliminating certain fruits and vegetables for any number of reasons. An example of this would be:

The Wrinkle Cure (15)

• Claims that increased insulin levels cause inflammation, which in turn damages skin and may cause degenerative diseases such as heart disease and cancer.

• Does advocate eating “antioxidant-rich” meals, but directs dieters to avoid “bad carbohydrates” which are high on the glycemic index (e.g., bananas, carrots, fruit juices, mangoes, papaya, and potatoes).

Summary of Recent Studies on Low-Carbohydrate Diets

New England Journal of Medicine (5-22-03)

A Randomized Trial of a Low-Carbohydrate Diet for Obesity (16)

• Study duration: 1 year

• Study participants: 63 obese men and women with random assignment to either a low-carbohydrate, high-protein, high-fat diet or a high-carbohydrate, low-fat (conventional) diet

• Weight loss was higher for the low-carb dieters at both 3 and 6 months, but there was no significant difference noted between the groups at 12 months (study’s end)

• High attrition rate in both groups (only 37 people completed the entire study)

A Low-Carbohydrate as Compared with a Low-Fat Diet in Severe Obesity (17)

• Study duration: 6 months

• Study participants: 132 severely obese men and women with a high prevalence of diabetes or the metabolic syndrome; randomly assigned to either a low-carbohydrate or low-fat diet

• Low-carb dieters lost more weight during the study than did the low-fat dieters

• Low-carb dieters also showed improvement in insulin sensitivity and triglyceride levels (the authors “cannot definitively conclude that carbohydrate restriction alone accounted for this independent effect.”)

• High attrition rate in both groups (only 79 people completed the entire study)

The American Journal of Cardiology (7-01-01)

Metabolic Effects of High-Protein, Low-Carbohydrate Diets (18)

• Low-carbohydrate diets produce initially greater weight loss due to a “diet-induced diuresis” or reduction of total body water content

• Long-term weight loss is purely dependent upon energy balance (calories in/calories out) and not the degree of carbohydrate restriction

• Claims unfavorable metabolic effects due to complications from: ketosis (incomplete metabolism of fatty acids), high fat and saturated fat intake, exclusion of fruits, vegetables & grains, and high protein intake

• Claims unfavorable long-term effects can be: development of nephrolithiasis (kidney stones), osteoporosis, and progression of chronic renal insufficiency

Other Nutrition/Health Related Organizations “Weigh In”

on

Low-Carbohydrate and/or Fad Diets

American Dietetic Association (ADA)



The 70,000 member strong organization of food and nutrition professionals reiterated, after the two NEJM studies came out in May 2003, that “there is no magic bullet to safe and healthful weight loss.” (19) A previous position statement on weight management to improve overall health endorses “a lifelong commitment to healthful lifestyle behaviors emphasizing sustainable and enjoyable eating practices and daily physical activity.” (20) They acknowledge that dietitians’ biggest challenge is to “teach persons how to be healthy without restriction and deprivation and to reverse the distorted cognitions regarding food as ‘good’ or ‘bad’.” ADA states they continue to recommend an eating plan based on complex carbohydrates (whole grains, fruits and vegetables), moderate in protein and relatively low in fat, coupled with physical activity for lifelong weight management.

American Heart Association (AHA)



The AHA has “declared war” on fad diets in part because some have falsely claimed to have earned AHA’s endorsement. They too maintain that there are no “magic formulas” for weight loss. With regard to high protein/high fat (low carbohydrate) diets, they remain especially concerned that these diets are too high in fat and saturated fat, and will lead to increased risk for heart attack and stroke. (21) AHA warns that weight loss recommendations should be “based on carefully controlled, long-term scientific studies by independent scientists and physicians.” They have created guidelines to use when evaluating a weight loss/management program, and have also developed the Eating Plan for Healthy Americans, which strives to help people achieve a healthy eating pattern. (22)

American Institute for Cancer Research (AICR)



The AICR spends a great deal of effort trying to combat the misinformation put forth by popular low-carbohydrate diets. A recent study they conducted shows that most Americans believe weight management is a matter of what you eat rather than how much you eat. Their big concern is that “the ‘all or nothing’ approach to carbohydrates is too simplistic and potentially dangerous.” (23) AICR recommends expending more calories than are consumed for weight loss, and that meals be comprised of 2/3 plant-based foods, and 1/3 animal protein for a healthful diet.

International Food Information Council (IFIC)



IFIC warns to “look before you leap” where fad diets are concerned, because they offer the quick-fix or magic bullet as a weight loss strategy, and then end up falling short. A major concern is the lack of concrete scientific research to support the claims popular diets are making. IFIC claims that low-carbohydrate diets are, “nothing more than low calorie diets in disguise, but with some potentially serious consequences.” (24) They have put together some Tips for Spotting Fad Diets in an attempt to help people evaluate potential weight loss plans. (24)

Center For Science in the Public Interest (CSPI)



In November 2002, CSPI devoted it’s Nutrition Action Health Letter cover story to exposing inaccuracies in the reporting of the July 7, 2002 New York Times Magazine article by Gary Taubes, “What if Its All Been a Big Fat Lie?” (25) Many of the top names in the nutrition and obesity fields who were interviewed for that article felt it was misleading and left the impression that they supported the Atkins diet. CSPI used their November issue as a forum for those experts to discuss their quotes in the context they were intended, and to challenge the major claims Taubes made in the original article. In the end, they clarified that most nutrition/obesity experts agree on: cutting saturated and trans fats, not overdoing carbohydrates (type matters), and looking for a weight loss strategy that works for you.

This backgrounder has been reviewed by Dr. Barbara J. Rolls, Guthrie Chair and Professor of Nutritional Sciences, The Pennsylvania State University. Dr. Rolls is a leading researcher in the field of obesity and sits on the Research Advisory Board for the Produce for Better Health Foundation.

Citations

1. USDA/DHHS. Nutrition and Your Health: Dietary Guidelines for Americans.

5th ed. Washington, DC: USDA; 2000. Home and Garden Bulletin No. 232.

2. “Obesity trends.” Centers for Disease Control and Prevention, National Center for Health Statistics. nccdphp/dnpa/obesity/trend/index.htm.

3. Produce for Better Health Foundation. State of the Plate: Study on America’s Consumption of Fruits and Vegetables, 2003, NPD National Eating Trends.

4. Messina M, et. al. Reductionism and the narrowing nutrition perspective: time for reevaluation and emphasis on food synergy. J Am Diet Assoc.2001;101:1416-19.

5. Davy BM and Melby CL. The effect of fiber-rich carbohydrates on features of Syndrome X. J Am Diet Assoc. 2003; 103:86-96.

6. Hu FB and Willett WC. Optimal diets for prevention of coronary heart disease. JAMA. 2002; 288:2569-78.

7. Fung TT, et. al. Association between dietary patterns and plasma biomarkers of obesity and cardiovascular disease risk. Am J Clin Nutr. 2001; 73:61-7.

8. Liu S, et. al. Relation between a diet with a high glycemic load and plasma concentrations of high-sensitivity C-reactive protein in middle-aged women. Am J Clin Nutr. 2002; 75:492-98.

9. “The glycemic index: what it is and what it is not.” American Institute for Cancer Research. fads/more7.html.

10. Atkins RC. Dr Atkins’ New Diet Revolution. New York: Avon Books, 1998.

11. Heller RF and Heller RF. The Carbohydrate Addict’s Diet. New York: Penguin Books, 1991.

12. Steward HL, Bethea MC, Andrews SS, and Balart LA. The New Sugar Busters! New York: Ballantine Publishing, 2003.

13. Agatston A. The South Beach Diet. New York: Rodale, 2003.

14. Sears B. A Week In The Zone. New York: Harper/Collins, 2000.

15. Perricone N. The Wrinkle Cure. New York: Warner Books, 2000.

16. Foster GD, et. al. A randomized trial of a low-carbohydrate diet for obesity.

N Engl J Med. 2003; 348:2082-90.

17. Samaha FF, et. al. A low-carbohydrate as compared with a low-fat diet in severe obesity. N Engl J Med. 2003; 348:2074-81.

18. Denke MA. Metabolic effects of high-protein, low-carbohydrate diets.

Am J Cardiol. 2001; 88:59-61.

19. New studies of low-carb diets “confirm what we already know—there is no magic bullet to safe and healthful weight loss.” American Dietetic Association Press Release, May 21, 2003. Public/Media/PublicMedia_16442.cfm.

20. Position of the American Dietetic Association: Weight management.

J Am Diet Assoc. 2002; 102:1145-55.

21. “USDA: the great nutrition debate.” American Heart Association Media Advisory. presenter.jhtml?identifier=3003.

22. “Eating plan for healthy Americans.” American Heart Association. presenter.jhtml?identifier=1330.

23. “Cancer experts combat misinformation about carbs with ‘grass roots’ approach.” American Institute for Cancer Research Press Release, March 7, 2003. presscorner/pubsearchdetail.lasso?index=1596.

24. “Fad diets: look before you leap.” Food Insight; Mar/Apr 2000. International Food Information Council. ific.proactive/newsroom/release.vtml?id=20581.

25. Liebman B. “The truth about the Atkins diet.” Nutrition Action Health Letter, 2002; 29:3-7. Center for Science in the Public Interest.

Low-Carbohydrate Diet

Detailed Q & A

What is carbohydrate (CHO)?

• The body’s main energy source; comes in the form of starches and sugars, as well as fiber, which is not digestible and therefore not considered an energy source.

• Easily converted to glucose during digestion; insulin response allows absorption of glucose into the cells of the body.

• Two types: complex CHO= whole grains, breads, cereals, pastas, fruits, and vegetables; simple CHO= sugars/nutritive sweeteners and sweets (e.g. candy, foods/beverages with added sugar); milk and fruits also contain some natural simple sugars.

• Typically comprises between 55 to 60% of total daily calories (roughly 275-300 grams CHO per day based on 2,000 calorie daily intake).

• A serving of fruit (or starchy vegetables) is typically 15 grams CHO, while a serving of vegetables is usually 5 grams CHO.

What are low-carbohydrate diets and how do they work?

• Popular diets that often severely restrict CHO intake and increase protein intake to induce weight loss.

• CHO intake restricted to 60 grams or less (a common level recommended by many popular low-CHO diets) per day, which is ~12% of total calories based on 2,000 calorie daily intake. Some diets advocate as little as 20 grams CHO (the equivalent in 1 ½ slices of bread) per day to start, and then gradually add small amounts back into the diet.

• This CHO restriction puts the body into “ketosis,” which forces it to burn fat and protein instead of carbohydrate for energy.

• Rely heavily on the insulin/obesity rationale—i.e., the more CHO that is eaten, the more insulin needed to respond; the more insulin produced, the more resistant cells become, resulting in more hunger and ultimate weight gain. Thus, the argument is that large, continually circulating levels of insulin in the blood promote obesity.

• To reinforce the insulin/obesity connection, CHO-containing foods, including fruits & vegetables, are ranked based on their glycemic index (GI). GI is a number that identifies how quickly a specific amount of CHO from a food will affect blood sugar levels.

What is the argument against low-carbohydrate diets?

• Restricting CHO in the diet simultaneously imposes a restriction on the nutrients (vitamins, minerals and fiber) and phytochemicals found in many plant-based foods that are known to have health-promoting and disease-preventing properties.

• In spite of some fruits and vegetables having high GI’s, in general, all fruits and vegetables have a low glycemic load (GL)—defined as GI multiplied by CHO content. This means that fruits and vegetables do not contain much CHO and therefore are unlikely to adversely impact blood sugar management.

• Many health professionals/organizations dispute GI and the insulin/obesity connection. The American Diabetes Association does not endorse the use of GI in choosing foods to control blood sugar.

• Studies show CHO-restricted diets are not any more effective for “long-term” weight loss (i.e. after 12 months) than more “traditional” diets are.

• Major concerns about low-CHO diets include: the high protein intake puts more stress on the kidneys—what are the long-term effects?; and, what are the effects of prolonged decreased vitamin, mineral, fiber and phytochemical intake on overall health?

What does PBH endorse?

Eating low-fat meals that include 5 to 9 servings of colorful fruits and vegetables every day is a cornerstone of a healthy life plan; physical activity is another cornerstone. A combination of physical activity and proper food intake can help with attaining and maintaining a healthy weight.

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