An increase in dietary protein improves the blood glucose response in persons with type 2 diabetes

Nutrition for Aging Cats and Dogs and the Importance of Body Condition

Before recommending a diet for a senior pet, a thorough nutritional evaluation should be completed. Although many middle-aged and older pets are overweight, a large percentage of geriatric cats and dogs have a low BCS. Approximately one third of cats older than 12 years of age may have a decreased ability to digest fat, whereas one in five may have a compromised ability to digest protein. Thus, appropriate diets for these two age groups may differ considerably. Mature (middle-aged) cats would likely benefit from a lower calorie food, whereas geriatric cats (>12 years of age) may need a highly digestible nutrient-dense diet. More than 40% of dogs between the ages of 5 and 10 years are overweight or obese. Such dogs may benefit from diets with lower fat and calories. Senior dogs also have an increased need for dietary protein, however. Therefore, healthy older dogs may benefit from diets with an increased protein-to-calorie ratio, providing a minimum of 25% of calories from protein. Common obesity-related conditions in dogs or cats include DM and OA. Diabetes differs between dogs and cats. Type I diabetes, common in dogs, seems to respond to fiber-enriched diets, whereas type II diabetes, common in cats, seems to benefit from high-protein and low-carbohydrate diets. OA, an inflammatory condition that occurs in approximately 20% of dogs, may benefit from weight management and nutrients that reduce the inflammatory responses, such as long-chain n-3 fatty acids.

Carbohydrate-restricted diets high in either monounsaturated fat or protein are equally effective at promoting fat loss and improving blood lipids

BACKGROUND

When substituted for carbohydrate in an energy-reduced diet, dietary protein enhances fat loss in women. It is unknown whether the effect is due to increased protein or reduced carbohydrate.

OBJECTIVE

We compared the effects of 2 isocaloric diets that differed in protein and fat content on weight loss, lipids, appetite regulation, and energy expenditure after test meals.

DESIGN

This was a parallel, randomized study in which subjects received either a low-fat, high-protein (LF-HP) diet (29 +/- 1% fat, 34 +/- 0.8% protein) or a high-fat, standard-protein (HF-SP) diet (45 +/- 0.6% fat, 18 +/- 0.3% protein) during 12 wk of energy restriction (6 +/- 0.1 MJ/d) and 4 wk of energy balance (7.4 +/- 0.3 MJ/d). Fifty-seven overweight and obese [mean body mass index (in kg/m(2)): 33.8 +/- 0.9] volunteers with insulin concentrations >12 mU/L completed the study.

RESULTS

Weight loss (LF-HP group, 9.7 +/- 1.1 kg; HF-SP group, 10.2 +/- 1.4 kg; P = 0.78) and fat loss were not significantly different between diet groups even though the subjects desired less to eat after the LF-HP meal (P = 0.02). The decrease in resting energy expenditure was not significantly different between diet groups (LF-HP, -342 +/- 185 kJ/d; HF-SP, -349 +/- 220 kJ/d). The decrease in the thermic effect of feeding with weight loss was smaller in the LF-HP group than in the HF-SP group (-0.3 +/- 1.0% compared with -3.6 +/- 0.7%; P = 0.014). Glucose and insulin responses to test meals improved after weight loss (P < 0.001) with no significant diet effect. Bone turnover, inflammation, and calcium excretion did not change significantly.

CONCLUSION

The magnitude of weight loss and the improvements in insulin resistance and cardiovascular disease risk factors did not differ significantly between the 2 diets, and neither diet had any detrimental effects on bone turnover or renal function.

Long-term effects of advice to consume a high-protein, low-fat diet, rather than a conventional weight-loss diet, in obese adults with type 2 diabetes: one-year follow-up of a randomised trial

AIMS/HYPOTHESIS

This study compared the long-term weight loss and health outcomes at 1-year follow-up, after a 12-week intensive intervention consisting of two low-fat, weight-loss diets, which differed in protein content.

METHODS

We randomly assigned 66 obese patients (BMI: 27-40 kg/m2) with type 2 diabetes to either a low-protein (15% protein, 55% carbohydrate) or high-protein diet (30% protein, 40% carbohydrate) for 8 weeks of energy restriction (approximately 6.7 MJ/day) and 4 weeks of energy balance. Subjects were asked to maintain the same dietary pattern for a further 12 months of follow-up.

RESULTS

The study was completed by 38 of the subjects, with equal dropouts in each group. At Week 64, weight reductions against baseline were -2.2+/-1.1 kg (low protein) and -3.7+/-1.0 kg (high protein), p<0.01, with no diet effect. Fat mass was not different from baseline in either group. At Week 12, both diets reduced systolic and diastolic blood pressure by 6 and 3 mm Hg respectively, but blood pressure increased more with weight regain during follow-up in the low-protein group (p< or =0.04). At Week 64, both diets significantly increased HDL cholesterol and lowered C-reactive protein concentrations. There was no difference in the urinary urea : creatinine ratio at baseline between the two groups, but this ratio increased at Week 12 (in the high-protein group only, p<0.001, diet effect), remaining stable during follow-up in both diets.

CONCLUSIONS/INTERPRETATION

A high-protein weight-reduction diet may in the long term have a more favourable cardiovascular risk profile than a low-protein diet with similar weight reduction in people with type 2 diabetes.

Metabolic response of people with type 2 diabetes to a high protein diet

Background

One of the major interests in our laboratory has been to develop a scientific framework for dietary advice for patients with diabetes. Knowledge regarding the metabolic consequences and potential effects on health of protein in people with type 2 diabetes has been a particular interest.

Results

We recently have completed a study in which dietary protein was increased from 15% to 30% of total food energy. The carbohydrate content was decreased from 55% to 40%, i.e. dietary protein replaced part of the carbohydrate. This resulted in a significant decrease in total glycohemoglobin, a decrease in postprandial glucose concentrations and a modest increase in insulin concentration. Renal function was unchanged.

Currently we also are determining the metabolic response to a diet in which the carbohydrate content is further decreased to 20% of total food energy. The %tGHb decrease was even more dramatic than with the 40% carbohydrate diet.

Conclusion

From these data we conclude that increasing the protein content of the diet at the expense of carbohydrate can reduce the 24-hour integrated plasma glucose concentration, at least over a 5-week period of time. The reduction was similar to that of oral agents. Renal function was not affected significantly. Thus, increasing the protein content of the diet with a corresponding decrease in the carbohydrate content potentially is a patient empowering way of reducing the hyperglycemia present with type 2 diabetes mellitus, independent of the use of pharmaceutical agents.

Effect of a high-protein, low-carbohydrate diet on blood glucose control in people with type 2 diabetes

There has been interest in the effect of various types and amounts of dietary carbohydrates and proteins on blood glucose. On the basis of our previous data, we designed a high-protein/low-carbohydrate, weight-maintaining, nonketogenic diet. Its effect on glucose control in people with untreated type 2 diabetes was determined. We refer to this as a low-biologically-available-glucose (LoBAG) diet. Eight men were studied using a randomized 5-week crossover design with a 5-week washout period. The carbohydrate:protein:fat ratio of the control diet was 55:15:30. The test diet ratio was 20:30:50. Plasma and urinary beta-hydroxybutyrate were similar on both diets. The mean 24-h integrated serum glucose at the end of the control and LoBAG diets was 198 and 126 mg/dl, respectively. The percentage of glycohemoglobin was 9.8 +/- 0.5 and 7.6 +/- 0.3, respectively. It was still decreasing at the end of the LoBAG diet. Thus, the final calculated glycohemoglobin was estimated to be approximately 6.3-5.4%. Serum insulin was decreased, and plasma glucagon was increased. Serum cholesterol was unchanged. Thus, a LoBAG diet ingested for 5 weeks dramatically reduced the circulating glucose concentration in people with untreated type 2 diabetes. Potentially, this could be a patient-empowering way to ameliorate hyperglycemia without pharmacological intervention. The long-term effects of such a diet remain to be determined.

Carbohydrate and weight control: where do we stand?

PURPOSE OF THE REVIEW

The Atkins diet has been criticized and vilified by much of the scientific community since it was proposed 30 years ago, because it challenged nutritional recommendations and dietary guidelines for a healthy diet. However, in spite of such recommendations the prevalence of obesity continues to rise. The present review evaluates recent scientific evidence and attempts to reach consensus on the confusion of weight-reducing diets.

RECENT FINDINGS

Many dietary macronutrient paradigms have been proposed for the treatment of obesity. Since obesity in its dynamic phase is the result of energy intake exceeding energy expenditure, intuitively to lose weight energy intake should be less than energy expenditure, and one might expect that the macronutrient composition of the diet would have very little, if any, effect. However, short- and long-term therapies with low-carbohydrate or high-protein diets appear to offer advantages over conventional weight-loss regimens for weight loss, body composition and cardiovascular risk factors.

SUMMARY

Low-carbohydrate, Atkins-type diets have been demonstrated to have positive effects on weight loss and biomarkers of cardiovascular risk, which has prompted some researchers to question the validity of present-day dietary guidelines. Although evidence is accumulating in their favour, the safety and efficacy of low-carbohydrate, high-protein diets needs further long-term verification.

High-Protein Weight Loss Diets and Purported Adverse Effects: Where is the Evidence?

Results of several recent studies show that high-protein, low-carbohydrate weight loss diets indeed have their benefits. However, agencies such as the American Heart Association (AHA) have some concerns about possible health risks. The purpose of this review is to evaluate the scientific validity of AHA Nutrition Committee's statement on dietary protein and weight reduction (St. Jeor ST et al. Circulation 2001;104:1869–1874), which states: "Individuals who follow these [high-protein] diets are risk for ... potential cardiac, renal, bone, and liver abnormalities overall. Simply stated, there is no scientific evidence whatsoever that high-protein intake has adverse effects on liver function. Relative to renal function, there are no data in the scientific literature demonstrating that healthy kidneys are damaged by the increased demands of protein consumed in quantities 2–3 times above the Recommended Dietary Allowance (RDA). In contrast with the earlier hypothesis that high-protein intake promotes osteoporosis, some epidemiological studies found a positive association between protein intake and bone mineral density. Further, recent studies studies suggest, at least in the short term, that RDA for protein (0.8 g/kg) does not support normal calcium homeostasis. Finally, a negative correlation has been shown between protein intake and systolic and diastolic blood pressures in several epidemiological surveys. In conclusion, there is little if any scientific evidence supporting above mentioned statement. Certainly, such public warnings should be based on a thorough analysis of the scientific literature, not unsubstantiated fears and misrepresentations. For individuals with normal renal function, the risks are minimal and must be balanced against the real and established risk of continued obesity.