Weight loss and metabolic benefits with diets of varying fat and carbohydrate content: separating the wheat from the chaff

At similar weight loss, dietary composition determines the degree of glycemic improvement in diet-induced obese C57BL/6 mice

Background

Achieving weight loss is the cornerstone of the treatment of the metabolic consequences of obesity, in particular of glucose intolerance.

Objective

To determine whether improvement in glucose control depends on dietary macronutrient composition of the diet at identical weight loss.

Materials and methods

Twenty-two weeks old diet-induced obese C57BL/6 mice lost weight through caloric restriction on normal chow (R-NC) or high fat diet (R-HF). Control mice were fed normal chow (LEAN) or high fat diet (OBESE) ad libitum. Body weight and composition were assessed after 8 weeks of dietary intervention. Glucose homeostasis was evaluated by intraperitoneal glucose tolerance tests (IPGTT). Epididymal white adipose (eWAT) and hepatic tissues were analyzed by immunohistochemistry and RT-qPCR.

Results

By 30 weeks of age, the body weight of the mice on R-NC (31.6±1.7g, mean±SEM) and R-HF (32.3±0.9g) was similar to LEAN mice (31.9±1.4g), while OBESE mice weighed 51.7±2.4g. Glucose tolerance in R-NC was better than in LEAN mice (69% AUC IPGTT, P 0.0168) whereas R-HF mice remained significantly less glucose tolerant (125% AUC IPGTT, P 0.0279 vs LEAN), despite identical weight loss. The eWAT pads and adipocyte size were similar in LEAN and R-NC mice, while the eWAT pad size of R-HF was 180% of R-NC (P < 0.0001) and the average adipocyte size of R-HF mice was 134% of R-NC fed mice (P 0.0285). No LEAN or R-NC mice had hepatic steatosis, in contrast to 28.6% of R-HF mice. Compared to OBESE mice, inflammatory markers were lower in eWAT and liver tissue of R-NC, but not in R-HF mice. Measures of visceral adiposity correlated well with glucose tolerance parameters.

Conclusions

In mice, caloric restriction on a normal chow diet improved glucose tolerance significantly more when identical weight loss was achieved on a high fat diet.

Inhibition of wheat bran and it's active compoments on α-glucosidase in vitro

Background:

Wheat bran is a traditional Chinese medicine; however, it is mostly used as feedstuff in China. Wheat bran is widely accepted as an important ingredient in many low-glycemic index foods in modern western societies; however, its glycemic control mechanism is unknown.

Objective:

To determine potent α-glucosidase inhibitory compounds from wheat bran and to identify the inhibition on α-glucosidase.

Materials and Methods:

Ethanolic extract of wheat bran was prepared to evaluate the inhibitory activity on α-glucosidase, then fractionation of the extract was guided by in vitro enzyme-inhibition assay, and the potent α-glucosidase inhibitory compounds were identified by high performance liquid chromatography and atmospheric pressure chemical ionization-mass spectrometry; finally the enzyme inhibition process was studied using the Michaelis-Menton and the Lineweaver-Burk equations.

Results:

Both baker's yeast and rat intestinal enzymes were mostly inhibited (87.9% and 66.8% inhibition, respectively) at concentration 0.6 mg/mL of the ethanolic extract of wheat bran. The petroleum ether fraction in the ethanolic extract of wheat bran showed significant activity against rat intestinal α-glucosidase, and revealed a dose-dependent effect. The inhibition was 76.57% at 0.3 mg/mL and 100% at 0.6 mg/mL. The active fraction 13 of petroleum ether fraction was identified as alkylresorcinols (ARs). ARs showed strong inhibition towards α-glucosidase and its IC₅₀ value was found to be 37.58 μg/mL. The enzyme kinetic studies showed that, in the presence of ARs, the Michaelis-Menton constant (K_m) remains constant whereas the maximal velocity (V_max) decreases, revealing a non-competitive type of inhibition.

Conclusion:

The therapeutic potentiality of ARs in the management of the postprandial hyperglycemia will proliferate the utilization of wheat bran in controlling type 2 diabetes.

Health effects of low-carbohydrate diets: where should new research go?

There has been considerable debate about the metabolic effects of restricting carbohydrate intake in weight and diabetes management. However, the American Diabetes Association has noted that weight and metabolic improvements can be achieved with low carbohydrate, low fat (implicitly higher carbohydrate), or a Mediterranean style diet (usually an intermediate level of carbohydrate). Our paper addresses variability in the definition for low or restricted carbohydrate, the effects of carbohydrate restriction on diabetes-related health outcomes, strategies for restricting carbohydrate intake, and potential genetic variability in response to dietary carbohydrate restriction. Issues for future research are also addressed.

A well-balanced diet combined or not with exercise induces fat mass loss without any decrease of bone mass despite bone micro-architecture alterations in obese rat

The association of a well-balanced diet with exercise is a key strategy to treat obesity. However, weight loss is linked to an accelerated bone loss. Furthermore, exercise is known to induce beneficial effects on bone. We investigated the impact of a well-balanced isoenergetic reducing diet (WBR) and exercise on bone tissue in obese rats. Sixty male rats had previously been fed with a high fat/high sucrose diet (HF/HS) for 4months to induce obesity. Then, 4 regimens were initiated for 2months: HF/HS diet plus exercise (treadmill: 50min/day, 5days/week), WBR diet plus exercise, HF/HS diet plus inactivity and WBR diet plus inactivity. Body composition and total BMD were assessed using DXA and visceral fat mass was weighed. Tibia densitometry was assessed by Piximus. Bone histomorphometry was performed on the proximal metaphysis of tibia and on L2 vertebrae (L2). Trabecular micro-architectural parameters were measured on tibia and L2 by 3D microtomography. Plasma concentration of osteocalcin and CTX were measured. Both WBR diet and exercise had decreased global weight, global fat and visceral fat mass (p<0.05). The WBR diet alone failed to alter total and tibia bone mass and BMD. However, Tb.Th, bone volume density and degree of anisotropy of tibia were decreased by the WBR diet (p<0.05). Moreover, the WBR diet had involved a significant lower MS/BS and BFR/BS in L2 (p<0.05). Exercise had significantly improved BMD of the tibia possibly by inhibiting the bone resorption, as evidenced by no change in plasma osteocalcin levels, a decrease of CTX levels (p<0.005) and trabecular osteoclast number (p<0.05). In the present study a diet inducing weight and fat mass losses did not affected bone mass and BMD of obese rats despite alterations of their bone micro-architecture. The moderate intensity exercise performed had improved the tibia BMD of obese rats without any trabecular and cortical adaptation.

A review of evidence-based strategies to treat obesity in adults

Obesity, with its comorbidities, is a major public health problem. Population-based surveys estimate 2 of every 3 U.S. adults are overweight or obese. Despite billions of dollars spent annually on weight loss attempts, recidivism is high and long-term results are disappointing. In simplest terms, weight loss and maintenance depend on energy balance, and a combination of increased energy expenditure by exercise and decreased energy intake through caloric restriction is the mainstay of behavioral interventions. Many individuals successfully lose 5%-10% of body weight through behavioral approaches and thereby significantly improve health. Similar success occurs with some weight loss prescriptions, although evidence for successful weight loss with over-the-counter medications and supplements is weak. Commercial weight loss programs have helped many individuals achieve their goals, although few programs have been carefully evaluated and compared, limiting recommendations of one program over another. For the very obese, bariatric surgery is an option that leads to significant weight loss and improved health, although risks must be carefully weighed. Lifestyle changes, including regular physical activity, healthy food choices, and portion control, must be adopted, regardless of the weight loss approach, which requires ongoing support. Patients can best decide the appropriate approach working with a multidisciplinary team, including their health care provider and experts in nutrition, exercise, and behavioral intervention.

Effects of different protein content and glycaemic index of ad libitum diets on diabetes risk factors in overweight adults: the DIOGenes multicentre, randomized, dietary intervention trial

BACKGROUND

Dietary regimens providing different levels of protein and glycemic index (GI) foods when prescribed for weight management may also influence insulin sensitivity.

PROCEDURES AND OUTCOMES

Overweight/obese adults in 8 European countries who lost ≥ 8% of initial body-weight (BW) after following a low calorie diet (LCD) were later randomly assigned with a 2x2 factorial design into 4 ad libitum dietary groups with two different protein content levels and dissimilar glycemic index, which were compared to a healthy reference diet. Specific markers assessing insulin resistance were measured. The LCD was initially applied to 932 adults and 773 were randomised to the 5 ad libitum diets. The 6-months programme was completed by 548 participants. The assignment to the Low Protein /High Glycemic Index diet induced a statistically higher HOMA-IR increase during the 6 months period as compared to the control. Contrariwise, the insulin response was lower in the High Protein/Low Glycemic Index diet after 60 and 90 min of an Oral Glucose Tolerance test subsequently carried out after the 6-months intervention. The Low Glycemic Index diets (either with high or low protein content) also lead to a decrease in fructosamine levels during the trial.

CONCLUSION/INTERPRETATION

After a weight loss period, an increase in the dietary protein proportions and a decrease in the consumption of foods with a high Glycemic Index within an ad libitum dietary intervention aiming to weight maintenance produced favorable effects on glycaemic control and insulin sensitivity in overweight/obese subjects.

Changes in body weight and metabolic indexes in overweight breast cancer survivors enrolled in a randomized trial of low-fat vs. reduced carbohydrate diets

Overweight status is common among women breast cancer survivors and places them at greater risk for metabolic disorders, cardiovascular morbidity, and breast cancer recurrence than nonoverweight survivors. Efforts to promote weight control in this population are needed. The objective of this research was to evaluate the effect of low-fat or low-carbohydrate diet counseling on weight loss, body composition, and changes in metabolic indexes in overweight postmenopausal breast cancer survivors. Survivors (n = 40) were randomized to receive dietitian counseling for a low-fat or a reduced carbohydrate diet for 6 mo. Weight and metabolic measures, including glucose, insulin, HbA1c, HOMA, lipids, hsCRP, as well as blood pressure were measured at baseline, 6, 12 and 24 wk. Dietary intake of fat and carbohydrate was reduced by 24 and 76 g/day, respectively. Weight loss averaged 6.1 (± 4.8 kg) at 24 wk and was not significantly different by diet group; loss of lean mass was also demonstrated. All subjects demonstrated improvements in total/HDL cholesterol ratio, and significant reductions in HbA1c, insulin, and HOMA. Triglycerides levels were significantly reduced only in the low-carbohydrate diet group (-31.1 ± 36.6; P = 0.01). Significant improvements in weight and metabolic indexes can be demonstrated among overweight breast cancer survivors adherent to either a carbohydrate- or fat-restricted diet.

Heart disease and stroke statistics--2011 update: a report from the American Heart Association

Each year, the American Heart Association (AHA), in conjunction with the Centers for Disease Control and Prevention, the National Institutes of Health, and other government agencies, brings together the most up-to-date statistics on heart disease, stroke, other vascular diseases, and their risk factors and presents them in its Heart Disease and Stroke Statistical Update. The Statistical Update is a valuable resource for researchers, clinicians, healthcare policy makers, media professionals, the lay public, and many others who seek the best national data available on disease morbidity and mortality and the risks, quality of care, medical procedures and operations, and costs associated with the management of these diseases in a single document. Indeed, since 1999, the Statistical Update has been cited more than 8700 times in the literature (including citations of all annual versions). In 2009 alone, the various Statistical Updates were cited ≈1600 times (data from ISI Web of Science). In recent years, the Statistical Update has undergone some major changes with the addition of new chapters and major updates across multiple areas. For this year’s edition, the Statistics Committee, which produces the document for the AHA, updated all of the current chapters with the most recent nationally representative data and inclusion of relevant articles from the literature over the past year and added a new chapter detailing how family history and genetics play a role in cardiovascular disease (CVD) risk. Also, the 2011 Statistical Update is a major source for monitoring both cardiovascular health and disease in the population, with a focus on progress toward achievement of the AHA’s 2020 Impact Goals. Below are a few highlights from this year’s Update.

Do obese patients after weight loss become metabolically normal?

OBJECTIVE

To compare the metabolic cardiovascular risk factors of obese patients after weight loss and 4-year weight loss maintenance afterwards against a matched control group of subjects with a stable body weight and without history of weight loss.

METHOD

50 obese non-diabetic subjects in the study group who previously lost 10% or more of their weight and afterwards entered a 4-year weight loss maintenance programme were matched by age, BMI and sex and compared to 50 weight-stable subjects without history of weight loss. The comparison between both groups was done in term of anthropometrical, metabolic and biological characteristics, early atherosclerosis and insulin sensitivity.

RESULTS

Anthropometrical, metabolic and biological characteristics were similar between the weight loss group and the control matched group. However, insulin sensitivity was still significantly lower in the weight loss than in the matched control group (p = 0.02). Intima media thickness (IMT) also was similar in both groups. We found that lower atherosclerosis measured by IMT at the level of the carotid is associated with better insulin sensitivity (p < 0.05). After the 4-year weight loss maintenance programme, insulin sensitivity improved in the post-weight loss group from 7.9 ± 3.2 to 8.4 ± 3.6 mg/kg/min.

CONCLUSION

All cardiometabolic parameters of obese subjects, except for insulin sensitivity, normalised completely after weight loss. The latter was improved by a weight loss maintenance programme if successfully completed.

Obesity and the metabolic syndrome: role of different dietary macronutrient distribution patterns and specific nutritional components on weight loss and maintenance

Weight loss and subsequent body weight maintenance are difficult for obese individuals despite the wide variety of dietary regimens and approaches. A substantial body of scientific evidence has shown that by simply varying the macronutrient distribution and composition of dietary factors, weight losses of varying amounts, longer-term body weight maintenance periods, better appetite regulation, and changes in features of the metabolic syndrome can be achieved. At present, renewed efforts are underway to increase the protein content of weight-loss diets, simultaneously restrict fat consumption to no more than 30%, favor polyunsaturated fat, have carbohydrates account for between 40 and 50% of total energy intake, and promote the consumption of low-glycemic foods. The present article reviews the scientific evidence for the effects of several dietary manipulations and sustainable strategies for weight loss and body weight stability as well as for treating specific features of the metabolic syndrome.

Diet and exercise in the prevention of diabetes

BACKGROUND

Individuals with impaired fasting glucose or impaired glucose tolerance are at high risk of progression to type 2 diabetes. Lifestyle modification through change to diet and exercise habit has considerable potential to prevent or delay the onset of this disease.

METHODS

A systematic literature search was undertaken of Medline, EMBASE, the Cochrane library and the Cumulative Index to Nursing and Allied Health Literature for journal articles relevant to the question of whether type 2 diabetes can be prevented by lifestyle change.

RESULTS

Four cohort studies in a total of 4864 high risk individuals followed for a period of 2.5-6 years were identified. These showed that lifestyle change may reduce the incidence of type 2 diabetes by 28-59%. Moreover, follow-up studies also indicate that diabetes incidence rates continue to be depressed many years after the discontinuation of a lifestyle intervention. Evidence from a meta-analysis confirms this evidence and suggests that it would be necessary to treat 6.4 (95% confidence interval 5.0-8.4) individuals to prevent or delay one case of diabetes through lifestyle intervention. An examination of weight loss diets (low fat, high protein or Mediterranean) suggests each may be effective but each has limitations requiring care in food selection. Evidence also suggests that the maintenance of weight loss also requires regular exercise with an additional expenditure of approximately 8.4 MJ week(-1) (2000 kcal week(-1)).

CONCLUSIONS

Diabetes can be prevented by lifestyle change. The challenge is to develop public health approaches to support individuals with respect to incorporating the lifestyle changes needed to reduce the risk of diabetes into their everyday life.

Obesity genes identified in genome-wide association studies are associated with adiposity measures and potentially with nutrient-specific food preference

BACKGROUND

New genetic loci, most of which are expressed in the brain, have recently been reported to contribute to the development of obesity. The brain, especially the hypothalamus, is strongly involved in regulating weight and food intake.

OBJECTIVES

We investigated whether the recently reported obesity loci are associated with measures of abdominal adiposity and whether these variants affect dietary energy or macronutrient intake.

DESIGN

We studied 1700 female Dutch participants in the European Prospective Investigation into Cancer and Nutrition (EPIC). Their anthropometric measurements and intake of macronutrients were available. Genotyping was performed by using KASPar chemistry. A linear regression model, with an assumption of an additive effect, was used to analyze the association between genotypes of 12 single nucleotide polymorphisms (SNPs) and adiposity measures and dietary intake.

RESULTS

Seven SNPs were associated (P < 0.05) with weight, body mass index (BMI), and waist circumference (unadjusted for BMI). They were in or near to 6 loci: FTO, MC4R, KCTD15, MTCH2, NEGR1, and BDNF. Five SNPs were associated with dietary intake (P < 0.05) and were in or near 5 loci: SH2B1 (particularly with increased fat), KCTD15 (particularly with carbohydrate intake), MTCH2, NEGR1, and BDNF.

CONCLUSIONS

We confirmed some of the findings for the newly identified obesity loci that are associated with general adiposity in a healthy Dutch female population. Our results suggest that these loci are not specifically associated with abdominal adiposity but more generally with obesity. We also found that some of the SNPs were associated with macronutrient-specific food intake.

A randomized controlled trial on the efficacy of carbohydrate-reduced or fat-reduced diets in patients attending a telemedically guided weight loss program

BACKGROUND

We investigated whether macronutrient composition of energy-restricted diets influences the efficacy of a telemedically guided weight loss program.

METHODS

Two hundred overweight subjects were randomly assigned to a conventional low-fat diet and a low-carbohydrate diet group (target carbohydrate content: >55% energy and <40% energy, respectively). Both groups attended a weekly nutrition education program and dietary counselling by telephone, and had to transfer actual body weight data to our clinic weekly with added Bluetooth technology by mobile phone. Various fatness and fat distribution parameters, energy and macronutrient intake, and various biochemical risk markers were measured at baseline and after 6, and 12 months.

RESULTS

In both groups, energy intake decreased by 400 kcal/d compared to baseline values within the first 6 months and slightly increased again within the second 6 months. Macronutrient composition differed significantly between the groups from the beginning to month 12. At study termination, weight loss was 5.8 kg (SD: 6.1 kg) in the low-carbohydrate group and 4.3 kg (SD: 5.1 kg) in the low-fat group (p = 0.065). In the low-carbohydrate group, triglyceride and HDL-cholesterol levels were lower at month 6 and waist circumference and systolic blood pressure were lower at month 12 compared with the low-fat group (P = 0.005-0.037). Other risk markers improved to a similar extent in both groups.

CONCLUSION

Despite favourable effects of both diets on weight loss, the carbohydrate-reduced diet was more beneficial with respect to cardiovascular risk factors compared to the fat-reduced diet. Nevertheless, compliance with a weight loss program appears to be even a more important factor for success in prevention and treatment of obesity than the composition of the diet.

TRIAL REGISTRATION

Clinicaltrials.gov as NCT00868387.

Influence of fat and carbohydrate proportions on the metabolic profile in patients with type 2 diabetes: a meta-analysis

OBJECTIVE

The effects of dietary macronutrient composition on metabolic profiles in patients with type 2 diabetes have been inconsistent. This meta-analysis aimed to elucidate the effect of replacing dietary fat with carbohydrate on glucose and lipid parameters in patients with type 2 diabetes.

RESEARCH DESIGN AND METHODS

We searched for randomized trials that investigated the effects of two kinds of prescribed diets (a low-fat, high-carbohydrate [LFHC] diet and a high-fat, low-carbohydrate [HFLC] diet); in these studies, energy and protein intake did not differ significantly between the two dietary groups. Nineteen studies that included 306 patients met our inclusion criteria. Median diet composition of carbohydrate/fat in the LFHC and HFLC diets was 58%/24% and 40%/40%, respectively.

RESULTS

Changes in values for A1C, fasting plasma glucose (FPG), and total and LDL cholesterol did not differ significantly between the LFHC and HFLC groups. However, the LFHC diet significantly increased fasting insulin and triglycerides by 8% (P = 0.02) and 13% (P < 0.001), respectively, and lowered HDL cholesterol by 6% (P < 0.001) compared with the HFLC diet. There were positive associations among the magnitude of changes in FPG, fasting insulin, and triglycerides for the diets analyzed. However, stratified analysis indicated that the increase in triglycerides was insignificant when accompanied by energy intake restriction.

CONCLUSIONS

Our findings suggested that replacing fat with carbohydrate could deteriorate insulin resistance while the adverse effect on triglycerides from the LFHC diet could be avoided by restricting energy intake to a degree sufficient for the attainment of weight reduction.

Contemporary strategies for weight loss and cardiovascular disease risk factor modification

Because of the overweight/obesity epidemic and attendant increase in risk of chronic disease worldwide, there is a pressing need to identify effective weight loss strategies. Current recommendations for weight loss advocate a reduced-calorie dietary pattern (lower in total fat) in conjunction with regular physical activity and behavior change. This combined approach is important for long-term adherence and weight maintenance. Several large-scale clinical trials implementing different reduced-calorie dietary patterns have shown that 4 to 10 kg of weight is typically lost. The different hypocaloric dietary patterns shown to be effective include reduced-fat diets (10%-30% of calories from fat), a Mediterranean-style diet, and diets that are reduced in energy density. The weight loss achieved is accompanied by beneficial changes in cardiovascular disease risk, including the lipid and lipoprotein profile and blood pressure. This article summarizes our current understanding of effective weight loss programs.