SCIENCE: ARTICLES & LIBRARY


The study objective was to evaluate the effect of prescribing a low-carbohydrate diet (LCD) and a low-fat diet (LFD) on food cravings, food preferences, and appetite   MORE
A single-center randomized trial at an academic medical center in Boston, Mass., studied the health effects of popular diets in overweight or obese adults (mean body mass index of 35; range, 27-42) aged 22 to 72 years with known hypertension, poor cholesterol profiles or high fasting blood sugar. A total of 160 participants were randomly assigned to either the Atkins, Zone, Weight Watchers or Ornish diet groups.

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Dietary protein intake and renal function

Recent trends in weight loss diets have led to a substantial increase in protein intake by individuals. As a result, the safety of habitually consuming dietary protein in excess of recommended intakes has been questioned. In particular, there is concern that high protein intake may promote renal damage by chronically increasing glomerular pressure and hyperfiltration. There is, however, a serious question as to whether there is significant evidence to support this relationship in healthy individuals. In fact, some studies suggest that hyperfiltration, the purported mechanism for renal damage, is a normal adaptative mechanism that occurs in response to several physiological conditions. This paper reviews the available evidence that increased dietary protein intake is a health concern in terms of the potential to initiate or promote renal disease. While protein restriction may be appropriate for treatment of existing kidney disease, we find no significant evidence for a detrimental effect of high protein intakes on kidney function in healthy persons after centuries of a high protein Western diet.

The electronic version of this article is the complete one and can be found online at:

http://www.nutritionandmetabolism.com/content/2/1/25/abstract

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Summary:

The following information was written by Atkins professionals.

The purpose of this study was to analyze the effects of a low-calorie, high-protein diet (using two different protein supplements) and resistance training (weight lifting), versus a low-calorie diet alone, on body composition changes in overweight police officers. The first group of 10 officers was placed on a low-calorie diet alone. The second group of 14 officers was placed on a low-calorie diet and given 1.5 grams per kilogram bodyweight per day of a casein protein supplement. The third group of 14 officers followed an identical regimen to the second but the supplement consumed was whey-based protein. Both groups 2 and 3 engaged in a resistance-training program in conjunction with their diet. Programs were maintained for 12 weeks. All groups lost an average of 5.5 pounds. At 12 weeks, the average percent body fat with diet alone decreased from 27% to 25%, the casein protein group decreased from 26% to 18% and the whey protein group from 27% to 23%. The average fat loss was 5.5, 15.4 and 9.3 pounds in the three groups respectively. Lean muscle mass gains did not occur in the group that was on a low-calorie diet alone. But the casein group had an average lean muscle mass gain of 8.8 pounds and the whey group an average increase of 4.4 pounds. Average increase in strength for chest, shoulder and legs was 59% for the casein group and 29% for the whey group, resulting in a significant difference as compared with the diet-only group. The researchers concluded that differences in body composition and strength are likely due to improved nitrogen retention (being in positive nitrogen balance, allowing for tissue building) and overall anticatabolic effects (prevention of muscle breakdown) caused by the casein proteins’ peptide (chains of amino acids that make up the protein) content.

 

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Summary:

The following information was written by Atkins professionals.

This study evaluated the effect a ketogenic diet had on the exercise capacity of eight healthy men. Subjects were placed in either a mixed diet group or a ketogenic group. The ketogenic diet consisted of 50% of calories derived from fat, 45% from protein and 5% from carbohydrate. After three days on the diet, subjects performed an exercise test in which they worked out at varying intensities. In comparison to subjects on the mixed diet, those on the ketogenic diet displayed increased maximal oxygen consumption (the amount of oxygen taken in by the lungs per minute, which is an excellent predictor of overall fitness). Moreover, the ketogenic subjects showed a decreased respiratory exchange ratio, meaning more fat was burned for energy. Finally, the ketogenic group showed a shift in the lactate threshold toward higher exercise loads. When the amount of lactate in the blood reaches a certain level at a certain intensity, performance is impaired; this point occurred after a longer duration of time at a higher intensity level of exercise. Blood lactic acid levels before and after exercise as well as blood pH were also lower. The ketogenic diet also lowered insulin concentration. The authors concluded that a short-term ketogenic diet does not impair, but in fact increases, aerobic exercise capacity, as indicated by an elevated maximal oxygen consumption and elevated lactate threshold.

 

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Summary:

 

The following information was written by Atkins professionals.

The aim of this study was to evaluate the effect of a high-protein intake compared with a “normal”-protein intake on energy substrate utilization (burning protein, fat or carbohydrate for energy). Fourteen men were placed on a standardized diet and exercise regimen for six days. Then, six of the men were placed in a “high-protein" group, lowering carbohydrate content from 58% to 33% (consuming 2.5 grams of protein per kilogram bodyweight) while eight were placed in a “normal-protein” group (consuming 1 gram of protein per kilogram of bodyweight). All subjects exercised for 90 minutes each day on a stationary bicycle. On days when their blood was tested, subjects engaged in two 90-minute bike workouts. When comparing diets, the high-protein, lower-carbohydrate group used more protein for energy during exercise. However, there was no effect on total 24-hour protein utilization. Subjects on the high-protein diet used more fat for energy during exercise as well as during recovery and at rest, compared with the “normal”-protein group. In addition to burning fat for energy, subjects on the high-protein lower- carbohydrate diet were also in positive nitrogen balance, which prevents the body from breaking down body tissue, such as muscle.

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Summary:

Abstract (provisional)

Background

Increasing evidence supports carbohydrate restricted diets (CRD) for weight loss and improvement in traditional markers for cardiovascular disease (CVD); less is known regarding emerging CVD risk factors. We previously reported that a weight loss intervention based on a CRD (% carbohydrate:fat:protein = 13:60:27) led to a mean weight loss of 7.5 kg and a 20% reduction of abdominal fat in 29 overweight men. This group showed reduction in plasma LDL-cholesterol and triglycerides and elevations in HDL-cholesterol as well as reductions in large and medium VLDL particles and increases in LDL particle size. In this study we report on the effect of this intervention with and without fiber supplementation on plasma homocysteine, lipoprotein (a) [Lp(a)], C-reactive protein (CRP), interleukin-6 (IL-6), and tumor necrosis factor alpha (TNF-alpha).

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Summary:

 

The following information was written by Atkins professionals.

This study sought to compare the effects of two weeks of a high-fat, low-carbohydrate diet (70% fat, 23% protein and 7% carbohydrate) with two weeks of a high-carbohydrate, low-fat diet (74% carbohydrate, 14% protein and 12% fat) on exercise performance. Five trained cyclists were required to perform a host of cycle tests at various intensities and lengths of time. Based on the results of these tests, exercise time to exhaustion during high intensity exercise was not significantly different between groups. However, when comparing the different diet groups’ performance during moderate intensity exercise, time to exhaustion was significantly longer after subjects followed the high-fat diet, despite starting off with lower muscle glycogen content (stored glucose). Subjects in the high-fat group also had a lower respiratory quotient, indicating that they were burning fat for fuel in place of carbohydrate.

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Ketogenic diets and physical performance

 

Impaired physical performance is a common but not obligate result of a low carbohydrate diet. Lessons from traditional Inuit culture indicate that time for adaptation, optimized sodium and potassium nutriture, and constraint of protein to 15–25 % of daily energy expenditure allow unimpaired endurance performance despite nutritional ketosis.

 

 

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Low-carbohydrate diets in the management of obese patients with type 2 diabetes seem intuitively attractive due to their potent antihyperglycemic effect.

We previously reported that a 20 % carbohydrate diet was significantly superior to a 55–60 % carbohydrate diet with regard to bodyweight and glycemic control in 2 non-randomised groups of obese diabetes patients observed closely over 6 months. The effect beyond 6 months of reduced carbohydrate has not been previously reported. The objective of the present study, therefore, was to determine to what degree the changes among the 16 patients in the low-carbohydrate diet group at 6-months were preserved or changed 22 months after start, even without close follow-up. In addition, we report that, after the 6 month observation period, two thirds of the patients in the high-carbohydrate changed their diet. This group also showed improvement in bodyweight and glycemic control.

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Two new studies presented at the Endocrine Society’s 91st Annual Meeting in Washington DC offer additional evidence for the value of a low-carb diet, not just for weight loss, but for overall health.   MORE
Disclaimer: Nothing contained on this Site is intended to provide health care advice. Should you have any health care-related questions, please call or see your physician or other health care provider. Consult your physician or health care provider before beginning the Atkins Diet as you would any other weight loss or weight maintenance program. The weight loss phases of the Atkins Diet should not be used by persons on dialysis or by pregnant or nursing women.