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Popular Weight Loss Diets: What’s The Evidence?

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Presentation on theme: "Popular Weight Loss Diets: What’s The Evidence?"— Presentation transcript:

1 Popular Weight Loss Diets: What’s The Evidence?
Low Carbohydrate Diets CJ Segal-Isaacson, EdD, RD High Protein Diets Manny Noakes, PhD Low Fat Diets Keith Ayoob, EdD, RD Application for CME credit has been filed with the American Academy of Family Physicians. Determination of credit is pending The AAFP is accredited by the Accreditation Council for Continuing Medical Education (ACCME) to sponsor Continuing Medical Education.

2 Focus of Each Talk: Define Diet
Present The Evidence for It’s Weight Loss Effects Present The Evidence for Cardiovascular and Insulin Sensitivity Effects Conclusions

3 Low Carbohydrate Weight Loss Diets
CJ Segal-Isaacson, EdD RD Assistant Professor Division of Nutrition and Health Behavior Department of Epidemiology and Population Health Albert Einstein College of Medicine, Yeshiva University

4 Cathy... On Low Carbohydrate Diets by Cathy Guisewite
Over the past couple of years there has been a revival in public interest about low carbohydrate diets...

5 Different Strokes For Different Folks
One size does not fit all with weight loss diets --- we need a variety of approaches to combat the obesity epidemic. It is possible that lower carbohydrate diets may be more effective for people with Metabolic Syndrome.1-2 Samaha FF, Iqbal N, Seshadri P, et al. N Engl J Med. May ; 348 (21): Eckel RH, Drazin B. J. Investigative Med. 51:Suppl ; S383.

6 Popular Low Carbohydrate Diets
The Dr. Atkins Diet (Has four levels): Induction (<20 g of carbs) Ongoing Weight Loss (Typically grams carbs) Premaintenance (Typically grams carbs) Maintenance (Typically grams carbs) Carbohydrate Addicts’ Diet Protein Power Cyclic Ketogenic The Zone Diet ( ) Neanderthin

7 2001 International Low Carbohydrate Weight Loss Survey*
Internet-based questionnaire. Data collected June-July 2001. 6,088 low carbohydrate dieters responded. *Segal-Isaacson CJ, Segal-Isaacson AE, Wylie-Rosett, J. The Journal of The American Dietetic Association : S45.

8 Who Responded To The Survey?
Questionnaire Was Web-based, With Online Consent Form SAMPLE SIZE: 6,088 “Low Carbers” Responded, June-July 2001 GENDER: 75.4% Women % Men RACE: 90.5% White 3.5% Hispanic % Black 3.3% Other MAIN GEOGRAPHIC LOCATIONS: 87.5% USA 0.5% Canada HIGHEST EDUCATIONAL DEGREE ATTAINED: 0.5% Elementary School 29.4% High School 21.3% Associates Degree 31.5% Bachelors Degree 13.0% Masters Degree 4.4% Doctoral Degree

9 The Three Most Common Low Carb Diets 2001 Low Carbohydrate Weight Loss Diet Survey)* N= 5177
*Segal-Isaacson CJ, Segal-Isaacson AE, Wylie-Rosett, J. The Journal of The American Dietetic Association : S45.

10 Typical Macronutrient Profile of Low Carbohydrate Diets
Nutrient Percentage of Calories Carbohydrate: 5-25% Protein: % Fat: % Alcohol: <5% (metabolized mostly as fat) Macronutrient percentages may distort what actually occurs in low carbohydrate dieting. Due to increased satiety, less food may be eaten. Carbohydrate intake is reduced while fat and protein intake may only moderately increase. Calories are often substantially reduced.

11 Typical Low Carbohydrate Dinner
Food Portion Size Calories Carbs (g) Fat (g) Protein (g) Roast Chicken 1/4 Chicken 306 19 31 Green Beans with Sunflower Seeds and Olive Oil 3/4 Cup 102 9 3 Green Salad with Italian Dressing 2 Cups with 1 Tablespoons 74 4 2 Diet Gelatin with Whipped Cream 1 Cup with 1 Tablespoon 70 6 TOTALS : 550 15 38 39

12 Foods On Low Carbohydrate Diets
Unrestricted Foods: Poultry, fish, meat, eggs, protein powders, low-starch vegetables, artificial sweeteners, diet gelatins, oils, butter. Mildly Restricted Foods: Cheeses, tofu, nuts, berries, yogurt, milk. Moderately Restricted Foods: Other fruits, cream, legumes, carbohydrate-reduced soy and grain products. Excluded Foods: Grains, bread, rice, potatoes, pasta, cereals, candies, pastries, cookies, pies.

13 Micronutrient Intake Generally adequate for most vitamins and minerals. If carbohydrates are severely restricted (<20 grams): Diet may be low in Vitamin C, Beta Carotene and Fiber. Potassium and sodium levels should be monitored and may need to be supplemented during the first month of the diet, as they are additionally excreted in urine.

14 And Talk About Ketogenic, Very Low Carbohydrate Diets
Let’s Switch Gears….. And Talk About Ketogenic, Very Low Carbohydrate Diets

15 The Role of Ketones In Human Physiology
Diets containing less than 10-15% carbohydrates usually cause modest amounts of urinary ketosis. Ketones are produced as fuel from metabolized fats (acetyl-CoA) when carbohydrate-dervived pyruvate is low. Enzymes are present within all cells to convert ketones into fuel except in erythrocytes, cornea, lens and retina. Adapted from a slide by Eric Westman, MD.

16 The Role of Ketones (continued)
Serum ketone levels are relatively low during low carbohydrate diets: Fed State mmol/L* Overnight Fast mmol/L Low Carb Ketogenic Diet 1-3 mmol/L** >20 Days Fasting 10 mmol/L Diabetic Ketoacidosis >25 mmol/L *Meckling et al. Can J Physiol Pharmacol 2002;80: ** Sharman MJ et al. J Nutr 2002;132: Adapted from a slide by Eric Westman, MD.

17 Short-Term Weight Loss Studies
Early studies comparing low carb to low fat diets often used caloric levels of <1000 cal/day. These very low calorie studies did not show a weight loss difference between diets.* Most comparison studies today are using diets with moderate calorie deficits of kcal/day. The carbohydrate intake in current studies is usually about that of the Atkins “Induction” Diet (most strict level) and is generally 30 g/day. *Yang MU, Van Itallie TB. J Clin Invest. Sep 1976;58(3):

18 Foster GD, Wyatt HR, Hill JO, et al. N Engl J Med
Foster GD, Wyatt HR, Hill JO, et al. N Engl J Med. May 22, 2003;348(21): First published RCT. Six month trial with follow-up to one year. Average baseline BMI of 34 kg/m2. Atkins Diet (all 4 levels) with ad lib kcal but controlled carbohydrate intake. Low cal diet kcal for women and kcal for men. Energy intake was 60% carb, 25% fat and 15% protein. N = 63; 43 women and 20 men. Low carb arm=33 and Low Cal arm=30. Average age is 44 years. No type 2 diabetes, lipid-lowering meds or other serious illness.

19 Weight Loss Results of Foster et al.
Better participant retention in low carb arm at all measurement points -- 3,6 & 12 months, p<0.05. Did not report on actual calorie intakes of subjects. Weight loss significantly better in low carb group at 3 and 6 months but not at 12 months: 3 Month Wt Loss: Low Carb ±5.0% Low Cal ± 3.7% (p<0.001). 6 Month Wt Loss: Low Carb ± 6.5% Low Cal ± 5.6% (p<0.02). 12 Month Wt Loss: Low Carb ± 6.7% Low Cal ± 6.3% (p<0.26).

20 Weight Loss Results of Foster et al.
From p of Foster et al., 2003 NEJM.

21 From p. 2088 of Foster et al., 2003 NEJM.
Lipid Results of Foster et al. From p of Foster et al., 2003 NEJM.

22 Blood Pressure and Insulin Sensitivity Results of Foster et al.
Equivalent improvements for both groups at 3,6 and 12 months for: Systolic and diastolic blood pressure. Area under the glucose curve (OGT). Area under the insulin curve (OGT). Insulin sensitivity.

23 Summary Of Results From Short-Term Studies
Low carb diets consistently produced more weight loss in RCTs that did not control the calorie levels between diets. Brehm BJ, Seeley RJ, Daniels SR, D'Alessio DA. J Clin Endocrinol Metab. Apr 2003;88(4): Foster GD, Wyatt HR, Hill JO, et al. N Engl J Med. May 22, 2003;348(21): Samaha FF, Iqbal N, Seshadri P, et al. N Engl J Med. May ;348(21): Westman EC, Yancy WS, Guyton JS. AHA. Nutrition Abstracts. Circulation (Supplement II). 2002;106(19).

24 Summary Of Results From Short-Term Studies cont.
In a recent study where the calories were kept the same, the weight loss was fairly comparable between the Atkins Diet and the DASH Diet although there was a trend for greater weight loss by 1.3 kg in the Atkins group. Due to the small sample size in each group (n=13) in the Atkins group and (n=12) in the DASH group, and the short time the results are not definitive. Stadler D, Burden V, McMurry M, Gerhard G, Connor W, Karanja N. Presentation at Experimental Biology annual conference, April, 2003. Current RCT trials at the Albert Einstein College of Medicine and Harvard University are also trying to answer the question of diet composition per se affects weight loss rates.

25 Summary Of Results From Short-Term Studies cont.
Low carbohydrate diets may produce more satiety and reduced appetite …. leading to decreased caloric intake. Increased satiety may explain generally lower drop- out rates in low carbohydrate groups. If there is increased satiety, is it due to protein? Brehm BJ, Seeley RJ, Daniels SR, D'Alessio DA. J Clin Endocrinol Metab. Apr 2003;88(4): Foster GD, Wyatt HR, Hill JO, et al. N Engl J Med. May 22, 2003;348(21): Samaha FF, Iqbal N, Seshadri P, et al. N Engl J Med. May ;348(21): Westman EC, Yancy WS, Guyton JS. AHA. Nutrition Abstracts. Circulation (Supplement II). 2002;106(19).

26 Summary Of Results From Short-Term Studies cont.
A low carbohydrate weight loss diet produced a greater reduction than a low fat weight loss diet in the inflammatory markers C-reactive protein and serum amyloid A. Both markers are associated with cardiovascular risk. Unclear whether the better reduction in inflammatory markers with the low carb diet was related to greater weight loss in the low carb group or was independent of this effect. O’Brien KD, Brehm BJ, Seeley RJ, Werner M, Daneils, D,D’Alessio DA. AHA. Nutrition Abstracts. Circulation .(Supplement II) ;106(19).

27 Summary Of Results From Short-Term Studies cont.
Preliminary evidence from 1 month study showed greater urinary acid and calcium excretion among overweight volunteers (BMI = 29.4 kg/m2) on a very low carbohydrate diet compared to their normal diet. Study found no metabolic acidosis. It did find increased urinary acid excretion that was due to the increase in sulfur-containing amino acids from protein foods and acidic ketone bodies. This may increase the risk of renal stones. Reddy ST, Wang CY, Sakhaee K, Brinkley L, Pak CY. Am J Kidney Dis. Aug 2002;40(2):

28 Summary Of Results From Short-Term Studies cont.
Increased calcium excretion without compensatory increase in intestinal calcium absorption may lead to bone loss. However, it’s unclear whether if a low carb diet was used for a longer time period, whether there might be physiological adaptation to it. Longer term studies are needed. Do populations such as the Eskimos who have survived on very low carb diets show such adaptations? Reddy ST, Wang CY, Sakhaee K, Brinkley L, Pak CY. Am J Kidney Dis. Aug 2002;40(2):

29 Summary Of Results From Short-Term Studies cont.
Low Carbohydrate Weight Loss Diets may work better for people with Metabolic Syndrome -- better weight loss, and greater improvements in triglyceride levels. Better weight loss tracks with insulin sensitivity improvements. Insulin sensitive participants lost more weight on the LF/HC diet compared to the HC/LC diet (13.56 ± kg compared to 6.12 ± 1.13 kg, p<0.01). Also there was a trend for improvements in insulin sensitvity in already IS participants on the LF/HC diet.

30 Summary Of Results From Short-Term Studies cont.
Insulin resistant participants lost more weight on the HF/LC diet compared to the LF/HC diet (11.46 ± kg compared to 6.52 ± 0.98 kg, p<0.05). Also there was a trend for improvements in insulin sensitvity in insulin resistant participants on the HF/LC diet. Samaha FF, Iqbal N, Seshadri P, et al. N Engl J Med. May ;348(21): Eckel RH, Drazin B. J. Investigative Med. 51:Suppl ; S383.

31 Summary Of Results From 2001 Low Carbohydrate Weight Loss Survey, N=6,088 Segal-Isaacson CJ, Segal-Isaacson AE, Wylie-Rosett, J. The Journal of The American Dietetic Association : S45. More than half of the respondents (55.9%) were currently dieting to lose weight and their BMI was higher than those who were not trying (31.2  7.8 compared to  7.6; p < ). Those who were not currently dieting to lose weight reported they had lost an average of 36.2  25.6 lbs but had wanted to lose 56.3  41.3 lbs. The amount of weight these respondents reported they kept off for at least one year was at least lbs for 53.2% of the respondents and at least lbs for 37.4% of the respondents.

32 Summary Of Results From 2001 Low Carbohydrate Weight Loss Survey cont.
Most respondents modified the diet they chose (60.2%). The most common modifications were adding more vegetables (29.0%), fruit (12.4%) or occasionally going off the diet (32.7%). The three most common diet likes were not feeling hungry (87.5%) or deprived (85.6%) and losing weight easily (74.1%). The three most common diet dislikes were bad breath (30.9%), light headedness (15.0%) and nausea (8.3%).

33 Current Low Carbohydrate Research At The Albert Einstein College of Medicine
The CCARB Study: First long-term study on low carbohydrate dieters. Internet-based -- will follow each participant for at least three years. More than 50% of participants have objectively documented their weight and height through their healthcare provider. Will also assess lipid values in a subset. Website address is: The Metabolic Impact Study: Pilot controlled feeding study that uses isocaloric-isonitrogenous diets to determine whether a very low carbohydrate diet burns body fat more quickly than a moderate low fat diet. Uses stable isotopes to trace whether ingested fats are oxidized or stored; indirect calorimetry to measure energy expenditure and and MRI to measure body fat distribution.

34 Current Low Carbohydrate Research At The Albert Einstein College of Medicine cont.
The Diabetes Dietary Study: Study on 74 adults with type 2 diabetes who also take insulin. Study will compare a one year trial of an Atkins-style low carbohydrate diet to the low fat diet used in the Diabetes Prevention Project. Call for more information on any of the three studies or at .

35 Annotated Bibliography

36 Brehm BJ, Seeley RJ, Daniels SR, D'Alessio DA.
J Clin Endocrinol Metab. Apr 2003;88(4): Six month RCT with 53 obese women comparing a low carb (<20 g/day for first two weeks then g/day) to a low calorie- 30% fat diet with calories at an estimate of resting energy expenditure. Weight loss was greater in the low carb group: 8.5 ± 1.0 kg compared to 3.9 ±1.0 kg. Blood pressure was normal in both groups and remained so during the trial. Lipids were normal in both groups but improved with weight loss in both groups. Fasting insulin and glucose decreased similarily in both groups.

37 Eckel RH, Drazin B. J. Investigative Med.51:Suppl 2.2003; S383.
Controlled 16 week feeding trial with 24 obese adults who were randomized to either a low fat/high carb or a high fat/low carb diet. Participants were also stratified by insulin levels: <10 U/ml = insulin sensitive; >15 U/ml = insulin resistant. Diets were matched for energy with a 400 kcal deficit. The composition of the low fat/high carb diet (LF/LC) was 60% CHO, 20% fat, 20% protein. The composition of the high fat/low carb diet (HF/LC) was 40% CHO, 40% fat, 20% protein. All participants lost at least 5.82 kg. Insulin sensitive participants lost more weight on the LF/HC diet compared to the HC/LC diet (13.56 ± 1.60 kg compared to 6.12 ± kg, p<0.01). Also there was a trend for improvements in insulin sensitvity in already IS participants on the LF/HC diet.

38 Eckel RH, Drazin B. J. Investigative Med.51:Suppl 2.2003; S383 cont.
Insulin resistant participants lost more weight on the HF/LC diet compared to the LF/HC diet (11.46 ± 1.37 kg compared to 6.52 ± kg, p<0.05). Also there was a trend for improvements in insulin sensitvity in insulin resistant participants on the HF/LC diet. There was no relationship between baseline fasting insulin levels and weight loss. The improvement in insulin sensitivity predicted the amount of weight loss, r=0.71. No significant changes in LDL or HDL. Triglycerides decreased in everyone but insulin resistant participants on the LF/HC diet. A high fat, low carbohydrate diet may be a more effective weight loss diet for insulin resistant obese people.

39 O’Brien KD, Brehm BJ, Seeley RJ, Werner M, Daneils,
D,D’Alessio DA. AHA. Nutrition Abstracts. Circulation (Supplement II). 2002;106(19). RCT of 43 obese adults comparing effects of low fat diet versus low carbohydrate diet on the inflammatory markers C-reactive protein and serum amyloid A. Six month trial with adlib diet. Low fat diet: n=22, Energy distribution = CHO 55%; Fat 30%; Protein 15% Low carb diet: n=21, Energy distribution = CHO <10%; no other restriction.

40 O’Brien KD, Brehm BJ, Seeley RJ, Werner M, Daneils,
D,D’Alessio DA. AHA. Nutrition Abstracts. Circulation (Supplement II). 2002;106(19). Continued. More weight loss in low carb group 6 months: -7.3 ± 4.7kg versus -2.8 ± 4.4 kg in low fat group. No reduction in inflammatory markers in low fat group but significant reduction in low carb group at 6 months: -33% reduction in CRP and -21% in serum amyloid A at 3 months. Unclear from abstract to what extent reduction in inflammatory markers was related to weight loss.

41 Reddy ST, Wang CY, Sakhaee K, Brinkley L, Pak CY.
Am J Kidney Dis. Aug 2002;40(2): Purpose of study was to evaluate the effect low carb, high protein diets on acid-base balance, calcium metabolism and stone formation. 10 volunteers with an average BMI of 29.4 kg/m2. Eight week trial: 2 weeks normal diet, 2 weeks at <20 g/day of carbs and 4 weeks at <35 g/day. No metabolic acidosis. Increased urinary acid excretion due to sulfer-containing amino acids from protein foods as well as acidic ketone bodies.

42 Reddy ST, Wang CY, Sakhaee K, Brinkley L, Pak CY.
Am J Kidney Dis. Aug 2002;40(2): Continued. Also Increased urinary calcium excretion without compensatory increases in intestinal calcium absorption. No changes in serum potassium, chloride, CO2, calcium or phosporus but slightly lower sodium levels. No change in urinary uric acid, oxalate, sodium, potassium or total volume of urine. Authors conclude the net increase in acid (50 mEq/d) through the combined effects of a high protein-low carbohydrate diet may increase risk for renal stones and bone loss.

43 Samaha FF, Iqbal N, Seshadri P, et al. N Engl J Med. May
;348(21): 132 severely obese adults with an average BMI of 43 kg/m2. 39% participants had diabetes and 43% metabolic syndrome. Six month RCT at a Phil. V.A. hospital. Low Carb: <30 g/day of carbs with no calorie restriction. Low Fat / LowCal: 30% dietary fat with 500 calorie deficit. Dietary compliance evaluated with 24 recalls.

44 Samaha FF, Iqbal N, Seshadri P, et al. N Engl J Med. May
;348(21): Continued. More weight lost on low carb diet: 5.8 ± 8.6 kg compared to 1.9 ± 4.2 kg; p=0.002. Triglycerides decreased more in the low carb group. No other lipid differences. Fasting glucose decreased more in low carb group among its diabetic subjects with concommittant reductions in DM meds. Insulin sensititivity improved more in low carb group (this was only measured in non-diabetic participants of both groups).

45 Stadler D, Burden V, McMurry M, Gerhard G,
Connor W, Karanja N. Presentation at Experimental Biology annual conference, April, 2003. Trial matched the caloric levels of 13 participants on the Atkins diet with another 12 participants on the DASH diet. The average ad lib calorie reduction on the Atkins diet was 68% of usual and the calorie intake of participants on the DASH diet was matched at 67% of usual. The participants were given meals prepared in a metabolic kitchen for 42 days. Although weight loss was not significantly different between the two diet groups, there was a trend for greater weight loss in the Atkins group by 1.3 kg.

46 Westman EC, Yancy WS, Edman JS, Tomlin KF, Perkins
CE. Am J Med. Jul 2002;113(1):30-36. One-armed trial. 41 of 51 adults (80%) completed six month study. Atkins Diet (adlib) with initially <25 g carbs + Atkins MVI suppl. Carbs increased to 50 g if 40% of wt loss achieved. Average weight loss 10.3 ± 5.9% p<0.001. Average fat loss of 2.9 ± 3.2% p<0.01 (skinfolds). Significant improvements in: systolic and diastolic BP, total cholesterol, LDL, triglycerides and HDL. Increases in urinary calcium and uric acid.

47 Westman EC, Yancy WS, Guyton JS. AHA. Nutrition Abstracts
Westman EC, Yancy WS, Guyton JS. AHA. Nutrition Abstracts. Circulation (Supplement II). 2002;106(19). Six month RCT comparing Atkins Diet (<20 g/day Carbs) to Low Fat/Low Cal Diet (no composition given in abstract). MVI, Borage, Flaxseed and Fish Oils supplements given to low carb group. Mean BMI of 34.5 kg/m2 at baseline. Low Carb Group, n= 36; Low Fat Group n = 27. Greater weight loss in low carb group: 13.8% to 8.8%. Reduction in VLDL greater in low carb group. Both groups had a 73% reduction in small LDL and an overall increase in LDL particle size. The low carb group had a larger increase in large LDL particles.

48 Popular Weight Loss Diets:
What’s The Evidence? Moderately High Protein Lower Carbohydrate (30% protein; <30% fat; 40% carbohydrate) Dr Manny Noakes Senior Research Dietitian CSIRO Clinical Research Unit Australia Health Sciences and Nutrition

49 Rationale for Moderately High Protein Intakes in Weight Loss?
Emerging scientific evidence for effects on satiety Dietary pattern that is nutritionally adequate

50 Emerging Scientific Evidence
Lean body mass spared - glucose tolerant women (Piatti et al,1994) Increased satiety - glucose tolerant women (Latner & Schwartz, 1999) Thermic effects - obese, hyperinsulinaemic men (Hwalla Baba et al,1999) High protein/Low GI -25% decrease in ad libitum intake – obese men (Dumesnil et al 2001) Thermic effect of HP meal 28% greater – no change in REE - Type 2 diabetes (Luscombe et al 2002) Endocrine and metabolic improvements - women with PCOS (Moran et al 2003)

51 Zone vs Atkins vs Conventional
Mean weight loss was 5.1 kg for those who completed the 12-week program. No significant differences in total weight, fat, or lean body mass loss by diet group. 91 commenced study and 49 completed the 12 weeks. Attrition was substantial for all plans Atkins 43%, Zone 60%, Conventional 36% Landers P J Okla State Med Assoc. 2002

52 Protein vs Carbohydrate in ad libitum Fat Reduced Diet
Skov et al 1999 High-carbohydrate (HC, protein 12% energy) n=25 High-protein (HP, protein 25% energy) n=25 RESULTS AFTER 6 MONTHS 5.1 kg in the HC group 8.9 kg in the HP group (P < 0.001) More subjects lost > 10 kg in the HP group (35% vs 9%). HP diet decreased fasting plasma triglycerides significantly.

53 Increased Protein/Carb ratio in overweight women
CHO/protein ratio 3.5 (CHO Group) 68g protein 1.4 (Protein group) 125g protein Layman et al J Nutr. 2003

54 Increased Protein/Carb ratio in overweight women
CHO/protein ratio 3.5 (CHO Group) 68g protein 1.4 (Protein group) 125g protein Layman et al J Nutr. 2003

55 Weight Loss Weight Loss
Weight Loss Maintenance HP Weight Loss Maintenance LP Interventions: Fat <30%, sat fat <10% 6500kJ High Protein (HP) - 28% E Protein, 42% E CHO Low Protein (LP) - 16% E Protein, 55% E CHO Parker B, Noakes M, Luscombe N, Clifton P. Diabetes Care. 2002

56 Foods HP diet LP diet Weetbix 1 Milk - 1% fat 250ml Skim milk powder
30g - Fruit Yoghurt - 0.1% fat 200g (7oz) Wholemeal bread 2 sl 3 sl Fruit 2 small 3 small Meat/fish/chicken 100g (3.5oz) Low kJ Vegetables <2.5 cups Cheese - 3% fat 60g (2oz) Rice 1 cup cooked Canola lite margarine 2 tsp 3 tsp Sunola oil Shortbread biscuits 3 4

57 Dietary Protein Effects in Type 2 Diabetes
Total fat mass significantly decreased in women on HP diet (12.4%) Abdominal fat mass significantly decreased in women on HP diet (12%) Significant decrease in LDL cholesterol levels on HP diet (5.7%) Parker B, Noakes M, Luscombe N, Clifton P. Diabetes Care. 2002

58 High Protein Diets and Renal Function in D2
Urinary albumin excretion was not affected by dietary protein during weight loss: n=19 with microalbuminuria HP diet: 24.2 to 19.8 mg/l (n=12) LP diet: 4.3 to 3.5 mg/l (n=7) Parker B, Noakes M, Luscombe N, Clifton P. Diabetes Care. 2002

59 High Protein Diets In Subjects With High Insulin
Diet effect p < 0.05 1 1.2 1.4 1.6 1.8 2 4 8 12 16 Week Triglycerides (mMol/L) High carb High Protein 9.6% 22.8% Farnsworth et al AJCN 2003

60 Insulin Response to Test Meals
Diet effect p < 0.05 20 40 60 80 100 120 140 30 180 Time (min) Insulin (mU/l) High Protein High Carb Farnsworth et al AJCN 2003

61 Glucose Response to Test Meals
Diet effect p = 0.020 4 5 6 7 8 9 30 60 120 180 Time (min) Glucose (mMol/l) High Protein High carb Farnsworth et al AJCN 2003

62 Aim: To compare a high protein weight loss diet with a high carbohydrate diet on weight loss and body composition nutrient status bone turnover markers measures of heart disease risk in women over 12 weeks… ..and subsequently follow up for 1 year Diets: 1. High carbohydrate 2. High protein, high red meat

63 109g protein 31g fat 161g carbohydrate
High Meat Protein 5600 KJ (1330 kcal) Cereal Low fat milk (250ml) 8oz Wholemeal bread (2 slices) Fruit (2) Beef/lamb 200g (7oz)- dinner Chicken/fish/meat 100g (3.5oz) lunch Vegetables 2.5 cups Diet Yoghurt 200g (7oz) Canola oil 3 tsp Wine 2 glasses/week (optional) 34% protein 20% fat 46% carbohydrate 109g protein 31g fat 161g carbohydrate

64 High Carbohydrate 5600 KJ (1330 kcal)
Cereal SKIM milk (250ml) 8oz Wholemeal bread (3 slices) Fruit (3) Chicken/pork/fish 80g - 3oz Vegetables 2.5 cups Canola oil 3 tsp Pasta/rice 120g/4oz cooked Low fat biscuits 3 Wine 2 glasses/week (optional) 17% protein 20% fat 64% carbohydrate 57g protein 31g fat g carbohydrate

65 Baseline characteristics by TG Status

66 Weight Loss by Triglyceride Status
Sig diet effect P=0.023 High protein High carb

67 Total And Midriff Fat Loss
Dexa Data * Sig diet effect High protein High carb

68 Triglycerides by TG status
HIGH TG Diet X TG interaction P=0.01 10% 28% LOW TG

69 (Effect of diet P=0.07, with overall ANOVA p=0.019)
after accounting for TG status

70 Significant effect of diet P=0.005 suggesting
lower energy intake on high protein diet

71 Calcium Excretion Calcium excretion decreased on both diets
reference range mmol/24hr Calcium excretion mmol/24hr week 0 week12 High protein High carb

72 Women with type 2 diabetes Subjects with elevated insulin levels
CONCLUSION There is emerging evidence that moderately high protein lower carbohydrate diets for weight loss are advantageous to conventional high carbohydrate diets for: Women with high TG Women with type 2 diabetes Subjects with elevated insulin levels There is no evidence that such moderate dietary patterns pose any health risks although more extended studies in overweight subjects with mild renal impairment are necessary to confirm safety in this group

73 Popular Weight Loss Diets: What’s the Evidence
Popular Weight Loss Diets: What’s the Evidence? Low-fat and Very Low-fat Diets Keith-Thomas Ayoob, EdD, RD, FADA Albert Einstein College of Medicine July 17, 2003

74 Macronutrient distribution
American Heart Association-style < 30% fat 15% protein 55% CHO Very low-fat diet 10-15% fat 12-15% protein 72-75% CHO

75 Typical dinner--AHA-style
3-oz. Broiled salmon 2/3 cup rice 1/2 cup mixed vegetables 1 cup salad greens, 2 tsp. Vinaigrette 1 slice whole wheat bread 1 tsp. butter 1/4 cantaloupe

76 Typical dinner--very low-fat
3-oz. baked whitefish 1-1/2 cups sauteed collard greens baked sweet potato 1/2 cup wild rice pilaf baked apple

77 Low-fat Diets: Weight Loss
2003 review by Pirozzo, et al Criteria for inclusion Randomized Ccontrolled Trial (RCT) of Low- Fat vs. other wt loss diets primary purpose was wt. Loss Age > 18 years & BMI > 25 at baseline Followed for at least 6 months “Low fat diet” = < 30% of calories from fat Pirozzo, S. et al. Cochrane Database of Systematic Reviews. 1, 2003.

78 Low-fat Diets: Weight Loss
Four 6-months studies Five 12-month studies Three 18-months studies Result: No significant differences compared to other weight loss diets

79 Low-fat Diets: Weight Loss
Meta-analysis of 34 studies, 2-12 months duration ad lib low-fat diets vs. controls Result: 3.3 kg loss in low-fat groups (sig.) Main factors: degree of dietary fat reduction pre-treatment body weight Astrup A, et al. Int J Obes Relat Met Dis Dec; 24(12):1545

80 Low-fat Diets: Long-term Success
Review by Ayyad & Anderson, 2000 Criteria for inclusion: adults Follow up of > 3 years Follow up of > 50% of original study group Criteria for long-term success: Maintain > 9-11 kg or all weight initially lost Ayyad C and Anderson T. Obesity Reviews, 2000; 1:113-9

81 Low-fat Diets: Long-term Success
Overall, 15% of followed-up subjects met criteria for success Diet alone = 15% met follow-up success Diet + group therapy = 27% met success Diet & behavior mod. = 14% met success Active follow-up better than passive for long term success (19% vs. 10%)

82 Low-fat diets vs. moderate/high-fat diets
12 month duration 4 DIETS: low-fat(LF) moderate fat(MF) mod fat-isocaloric(MF-iso) high fat(HF) weight, lipids, CV risk Fleming, RM. Preventive Cardiology. 5(3):110, 2002

83 RESULTS: Low-fat vs moderate & high-fat diets
% body weight lost at 12 months NS Wt loss associated with calories ONLY

84 Low-fat diets and satiety
Review of low-energy diets, glycemic index (GI), and obesity Low-GI foods = Increased satiety low-fat, low-GI-based diets = promote satiety and may therefore promote weight loss high-GI diets = weight gain and lower satiety Similar in animal studies Brand-Miller et al. Am J Clin Nutr. 76(1):281S, 2002 July

85 Long-term Compliance/Maintenance
McGuire et al random digit phone survey maintainers = lost > 10% of wt. , maintained for > 1 yr. 69 Maintainers, 56 regainers, 113 wt-stable controls McGuire et al. Int J of Ob & Rel Metab Disord: J of the Int Assoc Study of Ob. 23(12):1314, 1999 Dec

86 Long-term Compliance/Maintenance
Common factors for success: lower-fat intake than regainers/controls behavior strategies used more than regainers more physically active, esp. strenuous activity

87 National Weight Control Registry
Maintained a loss of > 25 lb. for > 1 year lost weight by different methods Maintainers: low fat, modest calorie intake Physically active 4-5 days/week

88 LF Diets and Drop-outs Problem in many studies
Most studies are 6 months or less Only count those who completed study Longer studies self-select Several studies do show compliance after 1 year Drop-out rate: 11-40% (Pirozzi, et al)

89 Lipids & low-fat diets Low calorie AND low/moderate fat:
significantly lower cholesterol, LDL-chol, TGs, TC/HDL ratios Low-calorie, high-fat diets, OR mod fat, isocaloric diets no significant changes:TG, TC, HDL, LDL-chol Fleming, RM. Preventive Cardiology. 5(3):110, 2002

90 C-reactive protein (CRP) & low-fat diets
CRP strongly associated with BMI LF diet (15% fat, 62% CHO) wks CRP significantly  with Low-Fat/low- calorie diet and wt loss Other dietary composition not investigated Heilbron et al. Arterioscl, Thromb & Vasc Biol. 21(6):968, 2001 June

91 LDL & low-fat diets 2001 review by Krauss
LDL-A = desirable large, fluffy LDL LDL-B = small, dense LDL (atherogenic) Conclusion: genes play a role LDL-B: benefits from a low-fat diet LDL-A: no benefits from low-fat diet IF isocaloric, & may convert to LDL-B profile CAVEAT: studies are often short-term, not all hi-CHO diets are alike Krauss. J of Nutr. 131(2) 340S; 2001 Feb

92 HDL & low-fat diets Meta-analysis of studies > 2months
LF diet lowered HDL, less so when fed ad lib than isoenergetically Epi studies consistently show populations with LF diets and low-HDL have LOW atherosclerosis Diets high in fruits, vegetables and grain fiber promote less atherosclerosis, cancer Jequier E and Bray G. Am J of Med. 113(9) supp. 2: Dec

93 Effect of type and amount of fat on HDL/lipids
Meta-analysis of 60 studies, Mensink et al Conclusion: Replacing fat with CHO isoenergetically may increase total/HDL ratio Replacing fat with CHO and reducing calories could have same effect as replacing SFA with MUFA and PUFA Replacing trans-fat with MUFA/PUFA had best effect on blood lipids Caveat: Results are general but the need is individual Mensink, RP et al. AM J Clin Nutr. 77(5); 1146, 2003 May

94 LF diets and insulin Review by Brand-Miller, et al
Low-fat, hi-CHO, hi-GI diets may increase insulin response BUT low-fat, low glycemic diets may promote wt loss via increased satiety, lowered insulin response Exercise improves insulin response Brand-Miller et al. Am J Clin Nutr. 76(1):281S, 2002 July

95 CONCLUSIONS Calories count more than fat: Low energy diets are more effective at producing weight loss than low-fat diets BUT low-fat diets may make it easier to reduce total energy intake

96 CONCLUSIONS Risks of Low-fat diets Benefits
Difficult long-term compliance on very low-fat diet increases with close follow-up and group support type of CHO may affect outcome, possibly by altering satiety Benefits Strong association with long-term maintenance LF, hi-CHO, hi-fiber diet reduces other health risks and is usually rich in vitamins, minerals, and phytonutrients

97 UNANSWERED QUESTIONS LONGER STUDIES NEEDED!
Do metabolic parameters show adaptation over time? Is long-term adaptation different? Should physical activity and/or metabolic profile affect recommendation of diet type?


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