The Truth About Low-Glycemic Diets

Healthy Eaters: Ignore Glycemic Index – 12/16/2014

The Truth About Low-Glycemic Diets | Johns Hopkins Medicine

Lawrence J. Appel, M.D., Ph.D.

Credit: Johns Hopkins Medicine

Fast Facts:

  • People eating a heart-healthy diet get no reduction in blood pressure or “bad” LDL cholesterol and no better insulin response when they choose low glycemic index foods.
  • Researchers say there is no need to worry about high versus low glycemic index foods when choosing a diet for heart health and reduced diabetes risk.
  • Other studies have not produced strong evidence that low glycemic foods help people lose weight or keep it off.

Good news for people who are already following a diet rich in fruits, vegetables and whole grains, and low in sweets: New research suggests these heart-healthy eaters don’t need to worry about choosing low glycemic index foods to lower the risk of diabetes and heart disease.

Though the study was not designed to test the effects of low glycemic index foods on weight control, its lead researchers looked at studies that did focus on weight and found no clear proof of a benefit.

The glycemic index is a measure of how quickly foods containing carbohydrates, such as fruits, cereals and baked goods, raise glucose levels in the bloodstream.

Conventional wisdom says that high glycemic index foods bananas and pasta are “bad” for heart health and may increase diabetes risk. But in a clinical trial reported Dec.

17 in the Journal of the American Medical Association, researchers at the Johns Hopkins University School of Medicine and Harvard Medical School found little evidence to support these claims.

Study volunteers followed carefully planned diets high or low in carbohydrates and with high or low glycemic index scores. Tests tracked the volunteers’ blood pressure, cholesterol levels and sensitivity to insulin at the beginning and end of each diet.

The results showed little difference between high and low glycemic index foods, says study co-director Lawrence J. Appel, M.D., M.P.H.

, a professor of medicine and director of the Welch Center for Prevention, Epidemiology and Clinical Research at Johns Hopkins Medicine.

“We were really surprised,” Appel says. “We did not detect any clear benefit of the low glycemic index diets on the major risk factors for heart disease, and we found no evidence of benefit for diabetes prevention.”

The authors looked closely at other studies focusing on the use of low glycemic index foods in weight control. “The evidence has been inconsistent that low glycemic foods help people lose more weight or keep it off,” Appel says. “In looking at the causes of obesity and ways to combat it, a narrow focus on the glycemic index seems to be unwarranted.”

Several popular diets recommend choosing carbohydrates that score low on the glycemic index, but that’s not always easy. Only laboratory tests can determine a food’s glycemic index, and the results can be unexpected: Apples score low, but cantaloupe scores high.

Appel and study co-director Frank M. Sacks, M.D., a professor of medicine at Harvard Medical School, wanted to find out whether foods’ glycemic index matters to heart health and diabetes prevention.

They recruited 163 volunteers from Baltimore and Boston — all of whom were overweight and had above normal blood pressure — and randomly assigned them to follow one of four diets.

Each diet contained the same number of calories, but those calories came from foods that were either high or low in carbohydrates, and also either high or low on the glycemic index. The volunteers ate the day’s main meal at a research center and took home their next two meals.

After five weeks on their assigned diets, the volunteers switched to a different one.

Researchers tested the volunteers’ blood pressure; sensitivity to insulin; and levels of “good” high-density lipoprotein (HDL) cholesterol, “bad” low-density lipoprotein (LDL) cholesterol and triglycerides — fat molecules, or lipids, that play a role in heart health. The low glycemic index diets did not lower blood pressure or LDL cholesterol, and they did not improve insulin resistance.

Women made up 51 percent of the study’s volunteers, and African-Americans made up 52 percent, so the results have broad relevance, says Appel, who offers simple advice for anyone overwhelmed by conflicting messages about diet and health.

“Get back to the basics that most people already know,” he says. “Don’t drink sugar-sweetened drinks. Try to eat fruits, vegetables and whole grains. Try to avoid sweets, salt, and foods high in saturated and trans fats. People who follow these principles will reap the benefits.”

Appel and Sacks led three earlier clinical trials that tested ways to reduce the risk of cardiovascular disease and diabetes, providing volunteers with carefully designed diets and measuring the effects on key health indicators. Their work established the health benefits of the DASH (Dietary Approaches to Stop Hypertension) and OmniHeart Mediterranean-style diets.

Other authors on the paper are Vincent Carey, Trisha Copeland and Benjamin Harshfield of Harvard Medical School; Edgar R. Miller III,  Jeanne Charleston, Phyllis McCarron and Karen White of the Johns Hopkins University School of Medicine; Nancy Laranjo, Janis Swain and Karen Yee of Brigham and Women’s Hospital; and Cheryl Anderson of the University of California, San Diego.

This work was supported by the National Heart, Lung and Blood Institute (grant number 5R01HL084568), the National Center for Research Resources (grant numbers 1 UL1 RR0275758-04 and M01-02635) and the National Center for Advancing Translational Science (grant number 8UL1 TR000170-05).

Source: https://www.hopkinsmedicine.org/news/media/releases/healthy_eaters_ignore_glycemic_index

The Truth About Low-Glycemic Diets | Johns Hopkins Medicine
Continue reading the main story

Low-carbohydrate diets have fallen in and favor since before the days of Atkins. But now an even stricter version of low-carb eating called the ketogenic diet is gaining popular attention, igniting a fierce scientific debate about its potential risks and benefits.

Both the Atkins and ketogenic diets encourage followers to cut carbs from their diets. But while the Atkins diet gradually increases carbs over time, keto places firm limits on carbs and protein.

This way of eating depletes the body of glucose, forcing it to primarily burn fat and produce an alternate source of fuel called ketones.

A typical ketogenic diet restricts carbs to less than 10 percent of calories and limits protein to 20 percent, while fat makes up the rest.

The keto diet has been popularized in best-selling books, promoted by celebrities and touted on social media as an antidote to various ailments. Proponents say it causes substantial weight loss and can help those with Type 2 diabetes dramatically improve their blood sugar levels, which fall when people avoid carbs.

There have been many studies of the ketogenic diet over the years, but most have been small and of fairly short duration. A federal registry of clinical research shows that more than 70 trials looking at the diet’s impact on brain, cardiovascular and metabolic health are either underway or in the beginning stages.

Dr. Ethan Weiss, a researcher and preventive cardiologist at the University of California, San Francisco, had long been skeptical of low-carb diets but decided to experiment with the ketogenic diet a couple years ago.

In a typical day he skips breakfast and eats mostly salads, nuts, cheese, roasted vegetables and grilled chicken, fish or tofu, as well as dark chocolate for dessert.

The result, he says: He lost 20 pounds and had to buy a new wardrobe.

“I haven’t felt this good since I was in high school,” he said.

Dr. Weiss subsequently started a company and a weight loss app with a former Weight Watchers vice president, raised $2.5 million from a group of Silicon Valley investors and started selling a $99 pen-size breathalyzer device, called Keyto, that allows users to measure their ketone levels and track how the diet is working for them.

“Our mission is to make doing this diet easier and more sustainable so people can make changes that allow them to lead a healthier lifestyle,” he said.

But the ketogenic diet has no shortage of detractors. Some doctors and health experts say it can lead to quick weight loss but that it is no more effective than other diets in the long term.

And many say they find it worrisome because it encourages foods high in saturated fat, which have been linked to heart disease, while restricting nutrient-rich foods supported by decades of research, beans, fruits, starchy vegetables and whole grains.

Last month, three doctors published an essay in JAMA Internal Medicine cautioning that the enthusiasm for the diet as a treatment for obesity and diabetes “outpaces” the evidence.

They pointed to studies suggesting that it had little advantage over lower fat diets for blood sugar control, and that it could cause adverse effects constipation, fatigue and, in some people, an increase in LDL cholesterol particles, a risk factor for heart disease.

“The greatest risk, however, of the ketogenic diet may be the one most overlooked: the opportunity cost of not eating high-fiber, unrefined carbohydrates,” the authors wrote. “Whole grains, fruits and legumes are some of the most health-promoting foods on the planet. They are not responsible for the epidemics of Type 2 diabetes or obesity, and their avoidance may do harm.”

Dr. Shivam Joshi, a co-author of the piece, said it generated a flood of emails from people across the globe. Some expressed praise and support, while others offered condemnation, a sign of just how polarizing the diet can be, said Dr. Joshi, an attending physician at NYC Health + Hospitals/Bellevue and a clinical assistant professor at New York University medical school.

“It’s a hot-button issue, and this paper struck a chord,” he added.

While the ketogenic diet can seem the latest in an endless stream of fad diets, it has a long history of therapeutic uses. Diabetics routinely practiced carb restriction before the discovery of insulin in the 1920s, and doctors at Johns Hopkins and other hospitals have used the diet for almost a century to reduce seizures in patients with epilepsy.

One of the benefits of carb restriction is that blood sugar levels remain stable after a meal, resulting in lower levels of insulin, a hormone that causes weight gain, said Dr. David Ludwig, an endocrinologist at Harvard Medical School and the author of a best-selling book on low-carb diets.

“Insulin is a Miracle-Gro for fat cells,” he said. “By lowering insulin levels, fewer calories from the meal may get stored in fat cells, leaving more to fuel metabolism and feed the brain. As a result, you may feel fuller longer after eating.”

In a series of studies over the years, Dr. Ludwig has found that low carb diets cause people to burn more calories and lose more weight compared to lower fat diets.

According to the carb and insulin theory of obesity, whole grains, starchy vegetables and tropical fruits are more healthful than processed carbs.

But they can still cause swings in blood sugar and insulin after a meal, and that can be particularly problematic for people with diabetes, said Dr. Ludwig.

In May, the American Diabetes Association published a consensus statement on nutrition strategies for people with diabetes.

It found that a variety of diets rich in unprocessed foods, the Mediterranean and vegetarian diets, could help people prevent and manage the disease.

But it also concluded that reducing overall carb intake “has demonstrated the most evidence” for improving blood sugar control.

“Carbohydrate is the macronutrient that most contributes to your blood sugar, and so it makes sense that reducing it is going to give you the biggest bang for your buck,” said the lead author of the report, Dr. William S. Yancy, Jr., an associate professor at Duke medical school and the director of the Duke Diet and Fitness Center.

But the carb and insulin explanation for obesity is the subject of much debate. Scientists at the National Institutes of Health have published research showing that people actually burn more calories on low-fat diets, and many experts contend that in the end, people will lose weight on any diet so long as they consume fewer calories.

Ultimately it is hard to reach definitive answers on any diet because nutrition studies tend to be short-term and not very rigorous, and there is tremendous variation in how people respond to different diets, said Dr. Steven B.

Heymsfield, the president of the Obesity Society and the director of the Body Composition-Metabolism Laboratory at the Pennington Biomedical Research Center in Baton Rouge, La.

Studies show that while some people who adopt a very low-carb diet experience a significant increase in their LDL cholesterol levels, for example, others see little or no change at all.

Dr. Heymsfield said he recommends a few things to people who try the ketogenic diet. He suggests limiting foods high in saturated fat butter, meat and cheese and focusing on foods with unsaturated fats olive oil, seafood, nuts, chicken and avocado. Consult a dietitian or doctor for their guidance, he said, and ask yourself if you are willing to commit to the diet for the long term.

“You have to set down a lifestyle and a healthy eating plan that you think you can adhere to for the rest of your life, because these things only work while you’re doing them,” he said.

“,”author”:”Anahad O’Connor”,”date_published”:”2019-08-20T09:00:03.000Z”,”lead_image_url”:”https://static01.nyt.com/images/2019/08/27/well/well-keto-diet/well-keto-diet-Jumbo.jpg”,”dek”:null,”next_page_url”:null,”url”:”https://www.nytimes.com/2019/08/20/well/eat/the-keto-diet-is-popular-but-is-it-good-for-you.html”,”domain”:”www.nytimes.com”,”excerpt”:”Low-carb, high-fat eating can lead to weight loss, but scientists debate the long-term effects on health.”,”word_count”:1271,”direction”:”ltr”,”total_pages”:1,”rendered_pages”:1}

Source: https://www.nytimes.com/2019/08/20/well/eat/the-keto-diet-is-popular-but-is-it-good-for-you.html

Effects of High vs Low Glycemic Index of Dietary Carbohydrate on Cardiovascular Disease Risk Factors and Insulin Sensitivity: The OmniCarb Randomized Clinical Trial

The Truth About Low-Glycemic Diets | Johns Hopkins Medicine

1. Wolever TM, Jenkins DJ, Jenkins AL, Josse RG. The glycemic index: methodology and clinical implications. Am J Clin Nutr. 1991;54(5):846–854. [PubMed] [Google Scholar]

2. Atkinson FS, Foster-Powell K, Brand-Miller JC. International tables of glycemic index and glycemic load values: 2008. Diabetes Care. 2008;31(12):2281–2283. [PMC free article] [PubMed] [Google Scholar]

3. Wolever TM, Gibbs AL, Mehling C, et al. The Canadian Trial of Carbohydrates in Diabetes (CCD), a 1-y controlled trial of low-glycemic-index dietary carbohydrate in type 2 diabetes: no effect on glycated hemoglobin but reduction in C-reactive protein. Am J Clin Nutr. 2008;87(1):114–125. [PubMed] [Google Scholar]

4. Reynolds RC, Stockmann KS, Atkinson FS, Denyer GS, Brand-Miller JC. Effect of the glycemic index of carbohydrates on day-long (10 h) profiles of plasma glucose, insulin, cholecystokinin and ghrelin. Eur J Clin Nutr. 2009;63(7):872–878. [PubMed] [Google Scholar]

5. Fabricatore AN, Ebbeling CB, Wadden TA, Ludwig DS. Continuous glucose monitoring to assess the ecologic validity of dietary glycemic index and glycemic load. Am J Clin Nutr. 2011;94(6):1519–1524. [PMC free article] [PubMed] [Google Scholar]

6. Livesey G, Taylor R, Hulshof T, Howlett J. Glycemic response and health: a systematic review and meta-analysis: relations between dietary glycemic properties and health outcomes. Am J Clin Nutr. 2008;87(1) suppl:258S–268S. [PubMed] [Google Scholar]

7. Appel LJ, Moore TJ, Obarzanek E, et al. DASH Collaborative Research Group. A clinical trial of the effects of dietary patterns on blood pressure. N Engl J Med. 1997;336(16):1117–1124. [PubMed] [Google Scholar]

8. Appel LJ, Sacks FM, Carey VJ, et al. OmniHeart Collaborative Research Group. Effects of protein, monounsaturated fat, and carbohydrate intake on blood pressure and serum lipids: results of the OmniHeart randomized trial. JAMA. 2005;294(19):2455–2464. [PubMed] [Google Scholar]

9. de Lorgeril M, Salen P, Martin JL, Monjaud I, Delaye J, Mamelle N. Mediterranean diet, traditional risk factors, and the rate of cardiovascular complications after myocardial infarction: final report of the Lyon Diet Heart Study. Circulation. 1999;99(6):779–785. [PubMed] [Google Scholar]

10. Estruch R, Ros E, Salas-Salvadó J, et al. PREDIMED Study Investigators. Primary prevention of cardiovascular disease with a Mediterranean diet. N Engl J Med. 2013;368(14):1279–1290. [PubMed] [Google Scholar]

11. Michaud DS, Fuchs CS, Liu S, Willett WC, Colditz GA, Giovannucci E. Dietary glycemic load, carbohydrate, sugar, and colorectal cancer risk in men and women. Cancer Epidemiol Biomarkers Prev. 2005;14(1):138–147. [PubMed] [Google Scholar]

12. White WB, Anwar YA. Evaluation of the overall efficacy of the Omron office digital blood pressure HEM-907 monitor in adults. Blood Press Monit. 2001;6(2):107–110. [PubMed] [Google Scholar]

13. Matsuda M, DeFronzo RA. Insulin sensitivity indices obtained from oral glucose tolerance testing: comparison with the euglycemic insulin clamp. Diabetes Care. 1999;22(9):1462–1470. [PubMed] [Google Scholar]

14. Gannon MC, Nuttall FQ, Westphal SA, Fang S, Ercan-Fang N. Acute metabolic response to high-carbohydrate, high-starch meals compared with moderate-carbohydrate, low-starch meals in subjects with type 2 diabetes. Diabetes Care. 1998;21(10):1619–1626. [PubMed] [Google Scholar]

15. Ludbrook J. Multiple inferences using confidence intervals. Clin Exp Pharmacol Physiol. 2000;27(3):212–215. [PubMed] [Google Scholar]

16. Jones G, Kenward MG. Design and Analysis of Cross-Over Trials. Second Ed. Boca Raton, FL: CRC Press; 2003. [Google Scholar]

17. Mensink RP, Katan MB. Effect of dietary fatty acids on serum lipids and lipoproteins: a meta-analysis of 27 trials. Arterioscler Thromb. 1992;12(8):911–919. [PubMed] [Google Scholar]

18. Obarzanek E, Sacks FM, Vollmer WM, et al. DASH Research Group. Effects on blood lipids of a blood pressure-lowering diet: the Dietary Approaches to Stop Hypertension (DASH) Trial. Am J Clin Nutr. 2001;74(1):80–89. [PubMed] [Google Scholar]

19. Sloth B, Krog-Mikkelson I, Flint A, et al. No difference in body weight decrease between a low-glycemic-index and a high-glycemic-index diet but reduced LDL cholesterol after 10-wk ad libitum intake of the low-glycemic-index diet. Am J Clin Nutr. 2004;80(2):337–347. [PubMed] [Google Scholar]

20. Hartman TJ, Albert PS, Zhang Z, et al. Consumption of a legume-enriched, low-glycemic index diet is associated with biomarkers of insulin resistance and inflammation among men at risk for colorectal cancer. J Nutr. 2010;140(1):60–67. [PMC free article] [PubMed] [Google Scholar]

21. Runchey SS, Pollak MN, Valsta LM, et al. Glycemic load effect on fasting and post-prandial serum glucose, insulin, IGF-1 and IGP-3 in a randomized, controlled feeding study. Eur J Clin Nutr. 2012;66(10):1146–1152. [PMC free article] [PubMed] [Google Scholar]

22. Sichieri R, Moura AS, Genelhu V, Hu F, Willett WC. An 18-mo randomized trial of a low-glycemic-index diet and weight change in Brazilian women. Am J Clin Nutr. 2007;86(3):707–713. [PubMed] [Google Scholar]

23. Vrolix R, Mensink RP. Effects of glycemic load on metabolic risk markers in subjects at increased risk of developing metabolic syndrome. Am J Clin Nutr. 2010;92(2):366–374. [PubMed] [Google Scholar]

24. Järvi AE, Karlström BE, Granfeldt YE, Björck IE, Asp NG, Vessby BO. Improved glycemic control and lipid profile and normalized fibrinolytic activity on a low-glycemic index diet in type 2 diabetic patients. Diabetes Care. 1999;22(1):10–18. [PubMed] [Google Scholar]

25. Shikany JM, Phadke RP, Redden DT, Gower BA. Effects of low- and high-glycemic index/glycemic load diets on coronary heart disease risk factors in overweight/obese men. Metabolism. 2009;58(12):1793–1801. [PMC free article] [PubMed] [Google Scholar]

26. Raatz SK, Torkelson CJ, Redmon JB, et al. Reduced glycemic index and glycemic load diets do not increase the effects of energy restriction on weight loss and insulin sensitivity in obese men and women. J Nutr. 2005;135(10):2387–2391. [PubMed] [Google Scholar]

27. McMillan-Price J, Petocz P, Atkinson F, et al. Comparison of 4 diets of varying glycemic load on weight loss and cardiovascular risk reduction in overweight and obese young adults: a randomized controlled trial. Arch Intern Med. 2006;166(14):1466–1475. [PubMed] [Google Scholar]

28. de Rougemont A, Normand S, Nazare JA, et al. Beneficial effects of a 5-week low-glycaemic index regimen on weight control and cardiovascular risk factors in overweight non-diabetic subjects. Br J Nutr. 2007;98(6):1288–1298. [PubMed] [Google Scholar]

29. Fabricatore AN, Wadden TA, Ebbeling CB, et al. Targeting dietary fat or glycemic load in the treatment of obesity and type 2 diabetes: a randomized controlled trial. Diabetes Res Clin Pract. 2011;92(1):37–45. [PMC free article] [PubMed] [Google Scholar]

30. Schwingshackl L, Hoffmann G. Long-term effects of low glycemic index/load vs high glycemic index/load diets on parameters of obesity and obesity-associated risks: a systematic review and meta-analysis. Nutr Metab Cardiovasc Dis. 2013;23(8):699–706. [PubMed] [Google Scholar]

31. Jebb SA, Lovegrove JA, Griffin BA, et al. RISCK Study Group. Effect of changing the amount and type of fat and carbohydrate on insulin sensitivity and cardiovascular risk: the RISCK (Reading, Imperial, Surrey, Cambridge, and Kings) trial. Am J Clin Nutr. 2010;92(4):748–758. [PMC free article] [PubMed] [Google Scholar]

32. Gögebakan O, Kohl A, Osterhoff MA, et al. DiOGenes. Effects of weight loss and long-term weight maintenance with diets varying in protein and glycemic index on cardiovascular risk factors: the diet, obesity, and genes (DiOGenes) study: a randomized, controlled trial. Circulation. 2011;124(25):2829–2838. [PubMed] [Google Scholar]

33. Jenkins DJ, Kendall CW, McKeown-Eyssen G, et al. Effect of a low-glycemic index or a high-cereal fiber diet on type 2 diabetes: a randomized trial. JAMA. 2008;300(23):2742–2753. [PubMed] [Google Scholar]

34. Selvin E, Steffes MW, Zhu H, et al. Glycated hemoglobin, diabetes, and cardiovascular risk in nondiabetic adults. N Engl J Med. 2010;362(9):800–811. [PMC free article] [PubMed] [Google Scholar]

35. Mirrahimi A, de Souza RJ, Chiavaroli L, et al. Associations of glycemic index and load with coronary heart disease events: a systematic review and meta-analysis of prospective cohorts. J Am Heart Assoc. 2012;1(5):e000752. [PMC free article] [PubMed] [Google Scholar]

36. Dong JY, Zhang L, Zhang YH, Qin LQ. Dietary glycaemic index and glycaemic load in relation to the risk of type 2 diabetes: a meta-analysis of prospective cohort studies. Br J Nutr. 2011;106(11):1649–1654. [PubMed] [Google Scholar]

37. Goff LM, Cowland DE, Hooper L, Frost GS. Low glycaemic index diets and blood lipids: a systematic review and meta-analysis of randomised controlled trials. Nutr Metab Cardiovasc Dis. 2013;23(1):1–10. [PubMed] [Google Scholar]

38. Brown L, Rosner B, Willett WW, Sacks FM. Cholesterol-lowering effects of dietary fiber: a meta-analysis. Am J Clin Nutr. 1999;69(1):30–42. [PubMed] [Google Scholar]

39. Thomas DE, Elliott EJ. The use of low-glycaemic index diets in diabetes control. Br J Nutr. 2010;104(6):797–802. [PubMed] [Google Scholar]

40. Ebbeling CB, Swain JF, Feldman HA, et al. Effects of dietary composition on energy expenditure during weight-loss maintenance. JAMA. 2012;307(24):2627–2634. [PMC free article] [PubMed] [Google Scholar]

41. Larsen TM, Dalskov SM, van Baak M, et al. Diet, Obesity, and Genes (Diogenes) Project. Diets with high or low protein content and glycemic index for weight-loss maintenance. N Engl J Med. 2010;363(22):2102–2113. [PMC free article] [PubMed] [Google Scholar]

42. Heilbronn LK, Noakes M, Clifton PM. The effect of high- and low-glycemic index energy restricted diets on plasma lipid and glucose profiles in type 2 diabetic subjects with varying glycemic control. J Am Coll Nutr. 2002;21(2):120–127. [PubMed] [Google Scholar]

Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4370345/

Healthy eaters: Ignore glycemic index, scientists say

The Truth About Low-Glycemic Diets | Johns Hopkins Medicine

Good news for people who are already following a diet rich in fruits, vegetables and whole grains, and low in sweets: New research suggests these heart-healthy eaters don't need to worry about choosing low glycemic index foods to lower the risk of diabetes and heart disease. Though the study was not designed to test the effects of low glycemic index foods on weight control, its lead researchers looked at studies that did focus on weight and found no clear proof of a benefit.

The glycemic index is a measure of how quickly foods containing carbohydrates, such as fruits, cereals and baked goods, raise glucose levels in the bloodstream.

Conventional wisdom says that high glycemic index foods bananas and pasta are “bad” for heart health and may increase diabetes risk. But in a clinical trial reported Dec.

17 in the Journal of the American Medical Association, researchers at the Johns Hopkins University School of Medicine and Harvard Medical School found little evidence to support these claims.

Study volunteers followed carefully planned diets high or low in carbohydrates and with high or low glycemic index scores. Tests tracked the volunteers' blood pressure, cholesterol levels and sensitivity to insulin at the beginning and end of each diet.

The results showed little difference between high and low glycemic index foods, says study co-director Lawrence J. Appel, M.D., M.P.H.

, a professor of medicine and director of the Welch Center for Prevention, Epidemiology and Clinical Research at Johns Hopkins Medicine.

“We were really surprised,” Appel says. “We did not detect any clear benefit of the low glycemic index diets on the major risk factors for heart disease, and we found no evidence of benefit for diabetes prevention.”

The authors looked closely at other studies focusing on the use of low glycemic index foods in weight control. “The evidence has been inconsistent that low glycemic foods help people lose more weight or keep it off,” Appel says. “In looking at the causes of obesity and ways to combat it, a narrow focus on the glycemic index seems to be unwarranted.”

Several popular diets recommend choosing carbohydrates that score low on the glycemic index, but that's not always easy. Only laboratory tests can determine a food's glycemic index, and the results can be unexpected: Apples score low, but cantaloupe scores high.

Appel and study co-director Frank M. Sacks, M.D., a professor of medicine at Harvard Medical School, wanted to find out whether foods' glycemic index matters to heart health and diabetes prevention.

They recruited 163 volunteers from Baltimore and Boston — all of whom were overweight and had above normal blood pressure — and randomly assigned them to follow one of four diets.

Each diet contained the same number of calories, but those calories came from foods that were either high or low in carbohydrates, and also either high or low on the glycemic index. The volunteers ate the day's main meal at a research center and took home their next two meals.

After five weeks on their assigned diets, the volunteers switched to a different one.

Researchers tested the volunteers' blood pressure; sensitivity to insulin; and levels of “good” high-density lipoprotein (HDL) cholesterol, “bad” low-density lipoprotein (LDL) cholesterol and triglycerides — fat molecules, or lipids, that play a role in heart health. The low glycemic index diets did not lower blood pressure or LDL cholesterol, and they did not improve insulin resistance.

Women made up 51 percent of the study's volunteers, and African-Americans made up 52 percent, so the results have broad relevance, says Appel, who offers simple advice for anyone overwhelmed by conflicting messages about diet and health.

“Get back to the basics that most people already know,” he says. “Don't drink sugar-sweetened drinks. Try to eat fruits, vegetables and whole grains. Try to avoid sweets, salt, and foods high in saturated and trans fats. People who follow these principles will reap the benefits.”

Appel and Sacks led three earlier clinical trials that tested ways to reduce the risk of cardiovascular disease and diabetes, providing volunteers with carefully designed diets and measuring the effects on key health indicators. Their work established the health benefits of the DASH (Dietary Approaches to Stop Hypertension) and OmniHeart Mediterranean-style diets.

Story Source:

Materials provided by Johns Hopkins Medicine. Note: Content may be edited for style and length.

Source: https://www.sciencedaily.com/releases/2014/12/141216175709.htm

The Truth About Low-Carb Diets for Weight Loss

The Truth About Low-Glycemic Diets | Johns Hopkins Medicine

Cutting back on carbohydrates is nothing new. At the height of the Atkins craze in the early 2000s, a Gallup poll found that 27 percent of Americans said they were avoiding carbohydrates.

And while Atkins still has its devotees, other low-carbohydrate plans, Paleo, are getting more attention these days. The latest popular low-carb approach is the Ketogenic diet, a very low-carbohydrate, high-fat, moderate-protein plan.

The premise: Cut back on carbohydrates and sugars so that the body burns fat for fuel instead of carbs (its preferred source) in a metabolic state called ketosis.

People lost more weight and even improved their cholesterol more on a low-carb diet (defined as fewer than 40 grams of carbohydrates per day) compared with those on a low-fat diet, according to research published in the Annals of Internal Medicine from Tulane University. And a 2017 study published in the Journal of Medical Internet Research found that overweight adults with type 2 diabetes lost more weight and improved their blood sugar more on a ketogenic diet than on a conventional low-fat diabetes plan.

Eating fewer carbs and more protein may help to rein in your blood sugar—meaning, for most people, less hunger and cravings. “Low-carb diets make it a little bit easier to cut the calories and not be starving; they’re easier to stick to,” says Lawrence Cheskin, M.D.

, director of the Johns Hopkins Weight Management Center in Baltimore.

A ketogenic diet where most of the calories come from fat may drive up hunger initially, however, once that feeling subsides after about three weeks in, hunger levels decrease—along with weight—according to a 2017 study from Norway published in the International Journal of Obesity. 

Revert back to non-ketogenic eating after a period of time on the plan, according to the same Norwegian study, and feelings of hunger are ly to bounce back. The whole grains, legumes, and fruit that many people cut back on while on a low-carb diet are loaded with filling fiber and are consistently linked with decreased rates of heart disease, diabetes, and more.

Cheskin notes that people with type 1 (insulin-dependent diabetes) should not follow a ketogenic diet. What’s more, overdoing certain fat and protein sources can be problematic for many people.

“Some observational studies have found that people who consumed a diet with high amounts of animal protein and fat—mostly from red and processed meats—and relatively low amounts of carbs had increased risk of cardiovascular disease and mortality,” said Frank Hu, M.D., Ph.D.

, chair of the nutrition department at Harvard T.H. Chan School of Public Health in Boston.

Too much protein can also worsen kidney function in people who have kidney disease, which affects more than 30 million people in the U.S., most of whom don't know they have it, according to the National Kidney Foundation. People at risk for kidney problems include those with diabetes and high blood pressure.

Trim excess carbs, particularly sugars and other refined carbs such as white flour and white rice, to cut back on calories. Include protein from sources beans, fish, lean meats and poultry, and nuts and seeds in meals and snacks to help boost satisfaction.

Source: https://www.consumerreports.org/dieting-weight-loss/truth-about-low-carb-diets-for-weight-loss/