Moderate Protein Research Articles

The PREVIEW intervention study: Results from a 3‐year randomized 2 x 2 factorial multinational trial investigating the role of protein, glycaemic index and physical activity for prevention of type 2 diabetes

AimTo compare the impact of two long‐term weight‐maintenance diets, a high protein (HP) and low glycaemic index (GI) diet versus a moderate protein (MP) and moderate GI diet, combined with either high intensity (HI) or moderate intensity physical activity (PA), on the incidence of type 2 diabetes (T2D) after rapid weight loss.Materials and MethodsA 3‐year multicentre randomized trial in eight countries using a 2 x 2 diet‐by‐PA factorial design was conducted. Eight‐week weight reduction was followed by a 3‐year randomized weight‐maintenance phase. In total, 2326 adults (age 25‐70 years, body mass index ≥ 25 kg/m2) with prediabetes were enrolled. The primary endpoint was 3‐year incidence of T2D analysed by diet treatment. Secondary outcomes included glucose, insulin, HbA1c and body weight.ResultsThe total number of T2D cases was 62 and the cumulative incidence rate was 3.1%, with no significant differences between the two diets, PA or their combination. T2D incidence was similar across intervention centres, irrespective of attrition. Significantly fewer participants achieved normoglycaemia in the HP compared with the MP group (P < .0001). At 3 years, normoglycaemia was lowest in HP‐HI (11.9%) compared with the other three groups (20.0%‐21.0%, P < .05). There were no group differences in body weight change (−11% after 8‐week weight reduction; −5% after 3‐year weight maintenance) or in other secondary outcomes.ConclusionsThree‐year incidence of T2D was much lower than predicted and did not differ between diets, PA or their combination. Maintaining the target intakes of protein and GI over 3 years was difficult, but the overall protocol combining weight loss, healthy eating and PA was successful in markedly reducing the risk of T2D. This is an important clinically relevant outcome.

High Compared with Moderate Protein Intake Reduces Adaptive Thermogenesis and Induces a Negative Energy Balance during Long-term Weight-Loss Maintenance in Participants with Prediabetes in the Postobese State:A PREVIEW Study

Background:Weight loss has been associated with adaptations in energy expenditure. Identifying factors that counteract these adaptations are important for long-term weight loss and weight maintenance. Objectives:The aim of this study was to investigate whether increased protein/carbohydrate ratio would reduce adaptive thermogenesis (AT) and the expected positive energy balance (EB) during weight maintenance after weight loss in participants with prediabetes in the postobese state. Methods:In 38 participants, the effects of 2 diets differing in protein/carbohydrate ratio on energy expenditure and respiratory quotient (RQ) were assessed during 48-h respiration chamber measurements ~34 mo after weight loss.Participants consumed a high-protein (HP) diet (n = 20; 13 women/7 men; age: 64.0 ± 6.2 y; BMI: 28.9 ± 4.0 kg/m2)with 25:45:30% or a moderate-protein (MP) diet (n = 18; 9 women/9 men; age: 65.1 ± 5.8 y; BMI: 29.0 ± 3.8 kg/m2)with 15:55:30% of energy from protein:carbohydrate:fat. Predicted resting energy expenditure (REEp) was calculatedbased on fat-free mass and fat mass. AT was assessed by subtracting measured resting energy expenditure (REE)from REEp. The main outcomes included differences in components of energy expenditure, substrate oxidation, and ATbetween groups. Results:EB (MP = 0.2 ± 0.9 MJ/d; HP = –0.5 ± 0.9 MJ/d) and RQ (MP = 0.84 ± 0.02; HP = 0.82 ± 0.02) werereduced and REE (MP: 7.3 ± 0.2MJ/d compared with HP: 7.8 ± 0.2MJ/d) was increased in the HP group compared withthe MP group (P < 0.05). REE was not different from REEp in the HP group, whereas REE was lower than REEp in theMP group (P < 0.05). Furthermore, EB was positively related to AT (rs = 0.74; P < 0.001) and RQ (rs = 0.47; P < 0.01)in the whole group of participants. Conclusions:In conclusion, an HP diet compared with an MP diet led to a negative EB and counteracted AT ~34 mo after weight loss, in participants with prediabetes in the postobese state. These results indicate the relevance of compliance to an increased protein/carbohydrate ratio for long-term weight maintenance after weight loss. The trial was registered at clinicaltrials.gov as NCT01777893.

Ovariohysterectomy alters body composition and adipose and skeletal muscle gene expression in cats fed a high-protein or moderate-protein diet

The objective of this study was to measure changes in body composition, physical activity and adipose and skeletal muscle gene expression of cats fed a high-protein (HP) diet or moderate-protein (MP) diet, following ovariohysterectomy. Eight cats were randomized onto HP or MP diets and were fed those diets for several months prior to baseline. All cats underwent an ovariohysterectomy at baseline (week 0) and were allowed ad libitum access to dietary treatments for 24 weeks. Food intake was measured daily, and BW and body condition score were measured weekly. Blood, adipose and skeletal muscle tissue samples were collected, physical activity was measured, and body composition was determined using DEXA (dual-energy X-ray absorptiometry) at weeks 0, 12 and 24. Caloric intake increased soon after ovariohysterectomy, resulting in increased (P < 0.05) BW at weeks 12 and 24 compared to week 0. Body condition score and body fat percentage increased (P < 0.05) over time. Blood glucose increased (P < 0.05) linearly over time. Non-esterified fatty acids were decreased (P < 0.05) at weeks 12 and 24 compared to week 0. Blood leptin increased (P < 0.05) over time. Total physical activity decreased (P < 0.05) from week 0 to weeks 12 and 24 in all cats. Adipose tissue mRNA abundance of adiponectin, hormone sensitive lipase, toll-like receptor-4, uncoupling protein-2 (UCP2) and vascular endothelial growth factor decreased (P < 0.05) linearly over time, regardless of diet. Skeletal muscle mRNA abundance for glucose transporter-1, hormone sensitive lipase and UCP2 were decreased (P < 0.05), regardless of dietary treatment. Our research noted metabolic changes following ovariohysterectomy that are in agreement with gene expression changes pertaining to lipid metabolism. Feeding cats ad libitum after ovariohysterectomy is inadvisable.

Cats Are Able to Adapt Protein Oxidation to Protein Intake Provided Their Requirement for Dietary Protein Is Met

Cats require more dietary protein than noncarnivorous species. Earlier work showed that cats lack the ability to regulate hepatic urea cycle enzymes in response to dietary protein concentration. We thus hypothesized that cats are unable to fully adapt protein oxidation to protein intake, particularly at low-protein concentrations. We used indirect respiration calorimetry to assess cats’ ability to adapt substrate oxidation to diets containing different concentrations of protein, including 1 below their protein requirement. Nine cats (5 males and 4 females; 2.7 ± 0.5 y; 4.49 ± 0.19 kg) consumed each of 4 semipurified diets containing 7.5% [low protein (LP3)], 14.2% [adequate protein (AP)], 27.1% [moderate protein (MP)], and 49.6% [high protein (HP)] of metabolizable energy from protein in a modified crossover design, beginning with the MP diet and then consuming the remaining diets in random order. After adaptation to each diet, cats completed a 5-d nitrogen balance trial and at least 2 12-h indirect calorimetry measurements. There was a significant effect of diet on protein oxidation (P < 0.0001), which measured 10.4 ± 0.5, 14.1 ± 1.0, 25.0 ± 1.7, and 53.2 ± 1.7% of total energy expenditure for the LP, AP, M,P and HP diets, respectively. The ratio of protein oxidation:protein intake was higher with the LP diet (1.39 ± 0.07) than the other 3 diets (AP, 1.00 ± 0.07; MP, 0.93 ± 0.06; HP, 1.07 ± 0.03;P < 0.0001), indicating a net loss of protein with the LP diet. Thus, cats are able to adapt protein oxidation to a wide range of dietary protein concentrations, provided their minimum protein requirement is met.

Calciuric Effects of Short-Term Dietary Loading of Protein, Sodium Chloride and Potassium Citrate in Prepubescent Girls

Objective: Studies using adult human subjects indicate that dietary protein and sodium chloride have negative effects on the retention of calcium by increasing urinary calcium excretion, while alkaline potassium improves calcium retention along with decreasing urinary calcium losses. This study investigated the effect of these dietary factors on acute urinary calcium excretion in 14 prepubescent girls age 6.7 to 10.0 years.Methods: Subjects provided a fasting urine sample then consumed a meal containing one of five treatments: moderate protein (MP) providing 11.8 g protein, moderate protein plus 26 mmol sodium chloride (MP+Na), high protein (HP) providing 28.8 g protein, high protein plus 26 mmol sodium chloride (HP+Na), or high protein plus 32 mmol potassium as tripotassium citrate (HP+K). Urine was collected at 1.5 and 3.0 hours after the meal. Supplemental protein was given as 80:20 casein:lactalbumin. Test meals were isocaloric, and unless intentionally altered, components of interest except phosphate were equal between treatments. Each subject completed all five treatments.Results: Urinary calcium excretion rose after the meal, peaking at 1.5 hours. There were no significant differences in calcium excretion between treatments at any time point. The high protein treatments did not result in a significant increase in either net acid or sulfate excretion at 1.5 hours compared to moderate protein. Dietary sodium chloride had no effect on urinary sodium or calcium excretion over the 3 hours. After the potassium treatment, sodium excretion increased (p≤0.002) and net acid excretion decreased (p<0.001) compared to other treatments at 1.5 hours.Conclusions: In children, a simultaneous increase in protein and phosphorus due to increased milk protein intake did not increase acute urinary calcium excretion. An effect of dietary sodium chloride on acute urinary calcium excretion was not observed. Both these findings were similar to those of adult studies previously conducted in the same laboratory using similar format and treatments. Potassium citrate was not hypocalciuric in children, a response differing from that for adults, who have shown a decrease in acute urinary calcium excretion in response to alkaline potassium treatment. Further characterization of calciuric responses to dietary factors is required for children, who may differ from adults in many respects.

Effects of excess protein, sodium and potassium on acute and chronic urinary calcium excretion in young women

The extent to which chronic calciuric effects of excess protein, sodium and potassium were reflected in fasting and acute urinary excretion was determined in 10 healthy premenopausal women. Chronic excretion was measured after one week of stabilization to a high protein (HP) diet by adding 50 g protein (casein and lactalbumin, 80:20) to subjects' usual diets. Then, randomly, subjects received each of the following treatments added to a constant baseline diet in Weeks 2–4: HP, HP + 70 mmol KHCO 3 (HP+K), and HP (as casein only) + 70 mmol NaCl (HP+Na). In Week 5 subjects received the moderate protein (MP) treatment in which 50 g carbohydrate was given. Subjects provided 24-hour urine on Days 3 and 4 each week. Fasting blood and urine were obtained the morning of Day 5, after which the acute load study began. Subjects are meals containing one-third ( 1 3 ) of the respective treatment, followed by collection of timed urine and blood samples. In the chronic load study, calcium excretion was highest with HP+Na compared to MP and was intermediate with HP or HP+K treatment. Sodium and potassium excretion were reflective of the dietary intake. Net acid excretion was lowest when subjects were given added KHCO 3. Sulfate and phosphate excretion were highest during all of the HP treatments. Fasting sodium and calcium excretions were higher after chronic HP+Na or MP treatment compared to HP and HP+K. Acutely, incremental calcium excretion was higher for 1 3 HP+Na and also 1 3 MP . There was no hypercalciuria due to protein, nor hypocalciuria due to potassium. There was a modest hypercalciuric effect of sodium chloride. Comparing chronic effects to acute effects in this study of acclimated subjects, and to acute effects in unacclimated subjects from a previous study, similarities were observed. Thus acclimating subjects to treatment offers no benefit for studying diet-related effects on calcium excretion except to demonstrate a hypercalciuric effect of sodium chloride.

Protein supplementation of ammoniated wheat straw: effect on performance and forage utilization of beef cattle

We studied the effects of supplement CP concentration on performance and forage use of cattle allowed ad libitum access to ammoniated wheat straw. During two consecutive winters, crossbred beef cows in late gestation (n = 87 in 1990-1991, n = 84 in 1991-1992) were used in a randomized complete block design with three pens per treatment. Cows were stratified by weight, body condition score (BCS), age, and breed and randomly assigned within strata to 1) control (C, no supplement), or 2 kg/d of 2) low-protein (LP) supplement (12% CP), 3) moderate-protein (MP) supplement (20.1% CP), or 4) high-protein (HP) supplement (31.7% CP) (DM basis). The feeding period was 84 d in 1990-1991 and 60 d in 1991-1992. Supplementation (C vs LP, MP, or HP) increased (P < .01) cow weight gains (32.7 vs 60.7, 62.8, and 72.4 kg, respectively) and improved (P < .01) BCS. Calf birth weights, weaning weights, and ADG were not affected by treatment (P > or = .20). Average calving date, percentage of cows cycling at the start of the breeding season and percentage pregnant after a 60-d breeding season were also similar (P > .20) among treatments. Sixteen ruminally fistulated steers (482 kg, four steers per treatment) were blocked by weight and assigned to the same four supplements in a 30-d digestion trial. Supplementation increased (P < .01) digestible DMI and forage DMI (P < or = .04) and tended (P = .09) to increase digestible NDF intake but did not alter (P > or = .15) apparent DM or NDF digestibility.(ABSTRACT TRUNCATED AT 250 WORDS)

Potassium bicarbonate reduces high protein-induced hypercalciuria in adult men

The effect of adding sodium bicarbonate (NaHCO 3) and potassium bicarbonate (KHCO 3) on high protein-induced hypercalciuria was evaluated in eight healthy male subjects. Subjects were acclimated to high protein and then received in random order, each of the following supplements for four-day periods: 60 g protein (HP), 60 g protein + 90 mmol NaHCO 3 (HP+Na), and 60 g protein + 90 mmol KHCO 3 (HP+K). Subjects were then given a moderate protein (MP) diet. Subjects provided a 24-hour urine sample on Day 3 and Day 4, and a fasting urine and blood sample on Day 5, of each period. Day 3 and Day 4 calcium excretions were increased during the HP treatment as compared with the MP treatment. During the HP+K treatment, Day 3 and Day 4 calcium excretions were greatly reduced relative to the HP treatment. In contrast, during the HP+Na treatment, calcium excretion was reduced relative to the HP treatment on Day 3, but not on Day 4. Serum calcium was significantly increased during the HP+K relative to the MP treatment. This study suggests that KHCO 3, but not NaHCO 3, consistently reduces high protein-induced hypercalciuria to levels seen during ingestion of a moderate protein diet.

Supplementation of dormant tallgrass-prairie forage: II. Performance and forage utilization characteristics in grazing beef cattle receiving supplements of different protein concentrations.

Two experiments were conducted to evaluate the influence of supplemental protein concentration on the intake and utilization of dormant range forage by beef cattle. In Exp. 1,97 pregnant Hereford x Angus cows (avg wt = 454 kg) were assigned randomly to three isocaloric treatment supplements: 1) low protein (LP), 13% CP; 2) moderate protein (MP), 25% CP; and 3) high protein (HP), 39% CP. In Exp. 2, 15 ruminally and 12 esophageally cannulated steers (avg wt = 319 and 355 kg, respectively) were assigned randomly to LP, MP and HP treatments and were used in a 22-d winter grazing trial to evaluate forage intake and utilization characteristics. In Exp. 1, cow body condition (BC) and BW changes responded in linear (P less than .01) and quadratic (P less than .01) fashions to increasing protein concentration, with MP and HP displaying the least BC and BW loss from trial initiation (d 1) through d 84. From d 84 to calving (avg calving date = d 120), only the HP supplement continued to be effective in minimizing BC loss (P less than .01). Calf birth weight tended (P = .17) to increase in a linear fashion to increasing supplemental protein concentration, but calf ADG and cow reproductive efficiency were unaffected (P greater than .10). In Exp. 2, forage OM intake responded in a quadratic fashion (P less than .10), with the MP treatment having the highest NDF digestibility and ruminal OM fill. In conclusion, beef cow BC and BW losses during the winter grazing period were minimized with increasing supplemental CP concentration. Intake and utilization of dormant forage by steers were improved with moderate (26%) levels of CP in the supplement.

Supplementation of dormant tallgrass-prairie forage: I. Influence of varying supplemental protein and(or) energy levels on forage utilization characteristics of beef steers in confinement.

Three experiments were conducted to evaluate effects of supplemental protein vs energy level on dormant forage intake and utilization. In Exp. 1, 16 ruminally cannulated steers were blocked by weight (avg wt = 242 kg) and assigned randomly to a negative control or to one of three isocaloric supplement treatments fed at .4% BW: 1) control, no supplement (NS); 2) 12% CP, low protein (LP); 3) 28% CP, moderate protein (MP); 4) 41% CP, high protein (HP). In Exp. 2 and 3, 16 ruminally cannulated steers were blocked by weight (avg wt = 332 kg, Exp. 2; 401 kg, Exp. 3) and assigned randomly to a 2 x 2 factorial arrangement of treatments. The treatments contrasted low (LP) and high (HP) levels of supplemental protein (.66 g CP/kg BW vs 1.32 g CP/kg BW) with low (LE) and high (HE) levels of supplemental ME (9.2 kcal/kg BW vs 18.4 kcal/kg BW). In Exp. 1, forage DMI as well as ruminal DM and indigestible ADF fill at 4 h postfeeding were greater (P less than .10) with the MP and HP steers than with control and LP steers. Total DM digestibility increased (P less than .10) for supplemented steers (35.5% for control vs 47.3 for supplemented steers); however, LP depressed (P less than .10) NDF digestibility. In Exp. 2, forage DMI, indigestible ADF flow and liquid flow were depressed (P less than .10) in LP-HE supplemented steers. In Exp. 3, HP steers had greater (P less than .10) forage DMI, indigestible ADF fill values (4 h postfeeding), liquid volume and tended (P = .11) to have greater ruminal DM fill (4 h postfeeding). In summary, increased levels of supplemental protein increased intake and utilization of dormant tallgrass-prairie forage (less than 3% CP). Increasing supplemental energy without adequate protein availability was associated with depressed intake and digestibility.

Riboflavin Status of Rats Fed Two Levels of Protein during Energy Deprivation and Subsequent Repletion

Adult male rats were fed either a low protein (LP) or moderate protein (MP) diet (0.6 and 1.8 g casein per rat per day, respectively) and 30 µg riboflavin (RF) while their energy intakes were progressively restricted to about 30% (26 kcal/day) of the predepletion ad libitum consumption. Total weight losses in 4 weeks averaged 17.3 ± 0.6 and 12.5 ± 0.7% from the initial body weights for the LP and MP groups, respectively, despite equal energy deprivation. Although liver riboflavin concentrations (micrograms/gram) were significantly higher in the energy-restricted groups than in either the predepletion or the ad libitum-fed control groups, total liver riboflavin remained at the predepletion level in both restricted groups. During energy deprivation, muscle riboflavin decreased significantly from the predepletion level and was not affected by protein intake. Subsequent repletion with 100 µg riboflavin/day and energy at the level voluntarily consumed by the LP group increased body and liver weights with both levels of protein, but liver riboflavin increased only in the MP group. Muscle riboflavin did not return to the predepletion level in either restricted group. Erythrocyte glutathione reductase activity coefficients remained normal for all groups during the depletion-repletion cycle.