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According to a commonly held view, the obesity pandemic is caused by overconsumption of modern, highly palatable, energy-dense processed foods, exacerbated by a sedentary lifestyle. However, obesity rates remain at historic highs, despite a persistent focus on eating less and moving more, as guided by the energy balance model (EBM). This public health failure may arise from a fundamental limitation of the EBM itself. Conceptualizing obesity as a disorder of energy balance restates a principle of physics without considering the biological mechanisms that promote weight gain. An alternative paradigm, the carbohydrate-insulin model (CIM), proposes a reversal of causal direction. According to the CIM, increasing fat deposition in the body-resulting from the hormonal responses to a high-glycemic-load diet-drives positive energy balance. The CIM provides a conceptual framework with testable hypotheses for how various modifiable factors influence energy balance and fat storage. Rigorous research is needed to compare the validity of these 2 models, which have substantially different implications for obesity management, and to generate new models that best encompass the evidence.

According to a commonly held view, the obesity pandemic is caused by overconsumption of modern, highly palatable, energy-dense processed foods, exacerbated by a sedentary lifestyle. However, obesity rates remain at historic highs, despite a persistent focus on eating less and moving more, as guided by the energy balance model (EBM). This public health failure may arise from a fundamental limitation of the EBM itself. Conceptualizing obesity as a disorder of energy balance restates a principle of physics without considering the biological mechanisms that promote weight gain. An alternative paradigm, the carbohydrate-insulin model (CIM), proposes a reversal of causal direction. According to the CIM, increasing fat deposition in the body—resulting from the hormonal responses to a high-glycemic-load diet—drives positive energy balance. The CIM provides a conceptual framework with testable hypotheses for how various modifiable factors influence energy balance and fat storage. Rigorous research is needed to compare the validity of these 2 models, which have substantially different implications for obesity management, and to generate new models that best encompass the evidence. [ABSTRACT FROM AUTHOR]

Background: The prevention and treatment of obesity is a public health challenge. Objective: We investigated the effects of dietary composition, insulin sensitivity (SI), and energy balance on predicted changes in body composition. Design: In a randomized crossover design study, 39 normal-weight (n = 23), overweight (n =8), and obese (n = 8) men and women (aged 25-36 y) each followed a 15-d isocaloric high-fat (HF; 50% fat) and high-carbohydrate [HC; 55% carbohydrate (CHO)] diet with a 4-6-wk washout period during the first year. During each treatment, energy balance was measured while the subjects were inactive by using indirect calorimetry on day 15, and SI was measured by using a euglycemic clamp study (40 mU . m-2. min-1) on day 16. Weight and body composition were then measured annually for 4 y. The outcomes for fat mass, percentage body fat, and weight were measured by using a linear 2-stage mixed model. Results: CHO balance (day 15) and SI (day 16) on the HC diet were highly and significantly correlated (r=0.55, P<0.001). On theHC diet, the subjects who had a higher positive CHO balance (day 15) gained less fat mass (P <0.001), percentage body fat (P < 0.006), and weight (P = 0.024) over time. When adjusted for SI, CHO balance remained a significant predictor of changes in fat mass (P= 0.021) and percentage body fat (P = 0.025). Conclusions: On a HC diet, the subjects who had a higher positive CHObalance on day 15 while they were inactive gained less fat mass during 4 y, a predictive effect independent of SI. As suggested in rodents, the capacity to expand the glycogen pool might reduce energy intake and protect against fat and weight gain. [ABSTRACT FROM AUTHOR]

Background: The influence of dietary carbohydrate glycemic index on blood lipids has not been well studied. Assessment of glycemic load is not usually included in a standard dietary analysis. Objective: The purpose of the present study was to examine relations between diet and blood lipids in youth with a broad range of cholesterol values and carbohydrate, fat, and protein intakes. Design: Relations between blood lipids and dietary constituents were examined in 32 healthy males and females aged 11-25 y. Subjects exhibited a range of LDL-cholesterol values (1.71- 6.67 mmol/L) and body mass index z scores (-1.18 to 2.64). Dietary constituents were assessed from 3-d food diaries. Results: The only significant correlations evident were negative correlations between HDL cholesterol and glycemic load (in relation to white bread), percentage carbohydrate, total dietary sugar, total carbohydrate, and fructose. On stepwise multiple regression analysis, glycemic load accounted for 21.1% of the variation in HDL cholesterol. Conclusions: Glycemic load appears to be an important independent predictor of HDL cholesterol in youth. This relation is of concern and suggests that dietary restrictions without attention to a possible resulting increase in glycemic load may result in an unfavorable influence on blood lipids. [ABSTRACT FROM AUTHOR]

Background: Type 2 diabetes is an epidemic that is affecting an ever-increasing proportion of the US population. Although consumption of refined carbohydrates has increased and is thought to be related to the increased risk of type 2 diabetes, the ecologic effect of changes in the quality of carbohydrates in the food supply on the risk of type 2 diabetes remains to be quantified. Objective: The objective was to examine the correlation between consumption of refined carbohydrates and the prevalence of type 2 diabetes in the United States. Methods: In this ecologic correlation study, the per capita nutrient consumption in the United States between 1909 and 1997 obtained from the US Department of Agriculture was compared with the prevalence of type 2 diabetes obtained from the Centers for Disease Control and Prevention. Results: In a univariate analysis, a significant correlation with diabetes prevalence was observed for dietary fat (r=0.84, P<0.001), carbohydrate (r = 0.55, P < 0.001), protein (r = 0.71, P < 0.001), fiber (r=0.16,P=0.03), corn syrup (r=0.83,P<0.001), and total energy (r = 0.75, P < 0.001) intakes. In a multivariate nutrientdensity model, in which total energy intake was accounted for, corn syrup was positively associated with the prevalence of type 2 diabetes (β = 0.0132, P = 0.038). Fiber (β=-13.86, P < 0.01) was negatively associated with the prevalence of type 2 diabetes. In contrast, protein (P=0.084) and fat (P=0.79) were not associated with the prevalence of type 2 diabetes when total energy was controlled for. Conclusions: Increasing intakes of refined carbohydrate (corn syrup) concomitant with decreasing intakes of fiber paralleled the upward trend in the prevalence of type 2 diabetes observed in the United States during the 20th century. [ABSTRACT FROM AUTHOR]

Background: Dietary fat content influences bile salt metabolism, but quantitative data from controlled studies in humans are scarce. Objective: The objective of the study was to establish the effect of dietary fat content on the metabolism of primary bile salts. Design: The effects of eucaloric extremely low-fat (0%), intermediatefat (41%; control diet), and extremely high-fat (83%) diets on kinetic values of cholate and chenodeoxycholate metabolism were determined after 11 d by using stable isotope dilution in 6 healthy men. All diets contained identical amounts of cholesterol. Results: The total primary bile salt pool size was not significantly affected by dietary fat content, although the chenodeoxycholate pool was significantly higher during the low-fat diet. Fractional turnover rates of both primary bile salts were 30-50% lower during the lowand high-fat diets than during the control diet. Total hepatic bile salt synthesis was ≈30% lower during both the high- and low-fat diets, but synthesis rates of the 2 primary bile salts were differentially affected. The molar ratio of cholate to total bile salt synthesis increased from 0.50 ± 0.05 (x≈ ± SD) to 0.59 ± 0.05 and 0.66 ± 0.04 with increasing fat intake, whereas the molar ratio of chenodeoxycholate to total bile salt synthesis decreased from 0.50 ± 0.05 to 0.41 ± 0.05 and 0.34 ± 0.04. The relative concentration of deoxycholate in plasma increased during the low-fat period, which indicated increased absorption from the colon. Conclusions: Both low- and high-fat diets reduce the synthesis and turnover rates of primary bile salts in humans, although probably through different mechanisms, and consequently they affect the removal of cholesterol from the body [ABSTRACT FROM AUTHOR]

Background: Data on the blood glucose response of diabetic patients to mixed meals containing food both rich in fiber and with a low glycemic index, such as dried peas, is scarce. Thus, the extent to which type 2 diabetic patients should take into account low-glycemic, high-fiber foods for their daily carbohydrate intake is uncertain. Objective: We compared the glycemic and insulinemic responses to 3 different meals based on dried peas, potatoes, or both in patients with type 2 diabetes undergoing dietary treatment. Design: The meals, prepared according to local recipes and consumed at weekly intervals in random order at lunchtime, contained comparabl,e amounts of carbohydrate, fat, protein, and water. The carbohydrate source of the meals differed and was supplied from either dried peas (meal 1), potatoes (meal 3), or a combination thereof (meal 2). Peripheral and venous blood was sampled over 180 min. Results: The increases in postprandial plasma glucose and insulin concentrations were delayed and significantly smaller after the pea meal than after the potato meal. The areas under the glucose curve were 164 ± 40, 257 ± 57, and 381 ± 40 mmol · 180 min/L for meals 1, 2, and 3, respectively (P < 0.01). The areas under the insulin curve were 13.8 ± 4.3, 15.4 ± 3.9, and 31.2 ± 6.9 nmol · 180 min/L, respectively (P = 0.0514). Conclusion: These findings suggest that carbohydrates in dried peas may be largely disregarded in carbohydrate counting and that type 2 diabetic patients should probably increase their consumption of low-glycemic, high-fiber foods at the expense of high-glycemic, low-fiber foods. [ABSTRACT FROM AUTHOR]

Background: Recent prospective data suggest that intake of rapidly digested and absorbed carbohydrates with a high dietary glycemic load is associated with an increased risk of ischemic heart disease. Objective: We examined whether a high dietary glycemic load was associated with elevated hs-CRP concentrations and whether this association was modified by body mass index (BMI; in kg/m2). Design: In 244 apparently healthy women, we measured plasma hs-CRP concentrations and determined average dietary glycemic loads with a validated semiquantitative food-frequency questionnaire. Using multiple regression models, we evaluated the association between dietary glycemic load and plasma hs- CRP after adjusting for age; treatment status; smoking status; BMI; physical activity level; parental history of myocardial infarction; history of hypertension, diabetes, and high cholesterol; postmenopausal hormone use; alcohol intake; and other dietary variables. Results: We found a strong and statistically significant positive association between dietary glycemic load and plasma hs-CRP. The median hs-CRP concentration for the lowest quintile of dietary glycemic load was 1.9 mg/L and for the highest quintile was 3.7 mg/L; corresponding multivariate-adjusted geometric means were 1.4 and 3.8 mg/L, respectively (P for trend < 0.01). This association was significantly modified by BMI. Among women with a BMI ≥ 25, the multivariate-adjusted geometric mean hs-CRP concentration in the lowest quintile was 1.6 mg/L and in the highest quintile was 5.0 mg/L; however, among women with a BMI < 25, the corresponding means were 1.1 and 3.1 mg/L, respectively (P = 0.01 for interaction). Conclusions: Dietary glycemic load is significantly and positively associated with plasma hs-CRP in healthy middle-aged women, independent of conventional risk factors for ischemic heart disease. Exacerbation of the proinflammatory process may be a mechanism whereby a high intake of rapidly digested and absorbed carbohydrates increases the risk of ischemic heart disease, especially in overweight women prone to insulin resistance. [ABSTRACT FROM AUTHOR]

Background: A high dietary fat intake is involved in the pathogenesis of insulin resistance. Objective: The aim was to compare the effect of different amounts of dietary fat on hepatic and peripheral insulin sensitivity. Design: Six healthy men were studied on 3 occasions after consuming for 11 d diets with identical energy and protein contents but different percentages of energy as fat and carbohydrate as follows: 0% and 85% [low-fat, high-carbohydrate (LFHC) diet], 41% and 44% [intermediate-fat, intermediate-carbohydrate (IFIC) diet], and 83% and 2% [high-fat, low-carbohydrate (HFLC) diet]. Insulin sensitivity was quantified by using a hyperinsulinemic euglycemic clamp (plasma insulin concentration: ≈190 pmol/L). Results: During hyperinsulinemia, endogenous glucose production was higher after the HFLC diet (2.5 ± 0.3 μmol⋅kg-1⋅min-1; P < 0.05) than after the IFIC and LFHC diets (1.7 ± 0.3 and 1.2 ± 0.4 μmol⋅kg-1⋅min-1, respectively). The ratio of dietary fat to carbohydrate had no unequivocal effects on insulin-stimulated glucose uptake. In contrast, insulin-stimulated, nonoxidative glucose disposal tended to increase in relation to an increase in the ratio of fat to carbohydrate, from 14.8 ± 5.1 to 20.6 ± 1.9 to 26.2 ± 2.9 μmol⋅kg-1⋅min-1 (P < 0.074 between the 3 diets). Insulin-stimulated glucose oxidation was significantly lower after the HFLC diet than after the IFIC and LFHC diets: 1.7 ± 0.8 compared with 13.4 ± 2.1 and 19.0 ± 2.1 μmol⋅kg-1⋅min-1, respectively (P < 0.05). During the clamp study, plasma fatty acid concentrations were higher after the HFLC diet than after the IFIC and LFHC diets: 0.22 ± 0.02 compared with 0.07 ± 0.01 and 0.05 ± 0.01 mmol/L, respectively (P < 0.05). Conclusion: A high-fat, low-carbohydrate intake reduces the ability of insulin to suppress endogenous glucose production and alters the relation between oxidative and nonoxidative glucose disposal in a way that favors storage of glucose. [ABSTRACT FROM AUTHOR]

To assess the advisability of using lactose-containing formulas in the rehabilitation of severely malnourished children, indices of clinical recovery, growth and restoration of body proteins and gastrointestinal function were measured longitudinally during the initial 45 days of hospitalization in 20 male, preschool children with kwashiorkor and marasmic-kwashiorkor. All patients received a diet based on cows' milk, but half were allocated to a formula pretreated with β-galactosidase to hydrolyze the lactose, while the others received the untreated, intact milk. The groups were identical with respect to clinical criteria on admission. For the final 37 days of the protocol, the subjects received 4 g of protein and 150 kcal of energy per kg per day. More diarrhea was experienced by the intact lactose group during early hospitalization. Overall, recovery was satisfactory in both cohorts, and there were no differences in rates of growth, body protein repletion, restoration of energy reserves nor intestinal functions. In conclusion, the routine reduction of lactose content from a milk-based diet for severe protein-energy malnutrition offers no advantages. [ABSTRACT FROM AUTHOR]

Two test meals, varying only in type of carbohydrate foods, were given to 12 volunteers with impaired glucose tolerance. The carbohydrate content of one meal was composed of potato and gelatin, while the other meals contained an equivalent amount of carbohydrate as rice and corn. The two meals were otherwise identical, and the additional constituents were turkey, green salad, and salad dressing. Plasma glucose and insulin responses were significantly lower after the meal containing rice and corn, with the change in the insulin response being the most dramatic. These results raise the possibility that variations in source of dietary carbohydrate may have therapeutic utility in patients with impaired glucose tolerance. [ABSTRACT FROM AUTHOR]

The most recent position statement on nutrition from the American Diabetes Association recommends an individualized approach to nutrition that is based on the nutritional assessment and desired outcomes of each patient and that takes into consideration patient preferences and control of hyperglycemia and dyslipidemia. To achieve these nutritional goals, either low-saturated-fat, high-carbohydrate diets or high-monounsaturated- fat diets can be advised. A meta-analysis of various studies comparing these two approaches to diet therapy in patients with type 2 diabetes revealed that high-monounsaturated-fat diets improve lipoprotein profiles as well as glycemic control. High--monounsaturated- fat diets reduce fasting plasma triacylglycerol and VLDL-cholesterol concentrations by 19% and 22%, respectively, and cause a modest increase in HDL-cholesterol concentrations without adversely affecting LDL-cholesterol concentrations. Furthermore, there is no evidence that high-monounsaturated-fat diets induce weight gain in patients with diabetes mellitus provided that energy intake is controlled. Therefore, a diet rich in cis-monounsaturated fat can be advantageous for both patients with type 1 or type 2 diabetes who are trying to maintain or lose weight. [ABSTRACT FROM AUTHOR]

Low concentrations of HDLs in plasma are a strong predictor of risk for coronary as well as other cardiovascular diseases. There is increasing evidence that this relation is causal and that interventions that change HDL concentrations also change risk. One such intervention is exchanging fat and carbohydrate. In controlled trials, low-fat, high-carbohydrate diets decrease HDL concentrations. The effect is strongest when carbohydrates replace saturated fatty acids, but is also seen when carbohydrates replace mono- and polyunsaturated fatty acids carbohydrates. The effect is seen in both short- and long-term trials and therefore appears to be permanent. This finding is supported by epidemiologic studies in which populations eating low-fat, high-carbohydrate diets were shown to have low HDL concentrations. Weight losses with consumption of low-fat diets could theoretically counter effects on HDL, but in published trials weight losses have been modest and insufficient to offset the decrease in HDL concentrations induced by carbohydrates. Thus, replacement of saturated fat by carbohydrates adversely affects plasma HDL concentrations; replacement of saturated fat by unsaturated fatty acids deserves consideration as an alternative. [ABSTRACT FROM AUTHOR]

Inpatient metabolic studies of human subjects were performed to obtain data on important nutritional issues. It was shown that wide variations in the ratio of carbohydrate to fat do not alter total 24-h energy need. Studies of the fatty acid composition of plasma low-density lipoproteins during low-fat feeding indicated that there can be considerable lipogenesis from carbohydrate in humans during isoenergetic feeding. The energy cost of this conversion must be small or be counterbalanced by other changes in energy metabolism because measured energy need was unaltered by fat-to-carbohydrate ratios. Energy need was, however, markedly varied by changes in body weight. Subjects at their usual body weights who had experimentally induced increases in body weight became inefficient and required a higher energy intake for weight maintenance. The reverse occurred with a reduction in body weight. The set point at which energy storage is defended is clearly different in obese persons. [ABSTRACT FROM AUTHOR]

We examined the relationship between diet composition and body fatness in 48 children (25 girls, 23 boys) aged 9-11 y. Subjects were identified for two study groups, non-obese [triceps skinfold (TSF) thickness < 85th percentile] and obese (TSF thickness 85th percentile). Measures for dietary intake, physical activity, resting energy expenditure (REE), and body composition were obtained by three 24-h dietary and activity recalls: indirect calorimetry: and anthropometrics, respectively. Percentage of body fat correlated positively with intakes of total (P < 0.0001), saturated (P < 0.01), monounsaturated (P < 0.0001), and polyunsaturated (P < 0.01) fatty acids, and negatively with carbohydrate intake (P < 0.001) and total energy intake adjusted for body weight (P < 0.001). After adjustment for study group, energy intake, REE, and physical activity, the associations remained for total, saturated, and monounsaturated fatty acid and carbohydrate intakes. These data suggest that diet composition, independent of total energy intake, REE, and physical activity may contribute to childhood obesity. [ABSTRACT FROM AUTHOR]

Diets rich in fat may promote obesity by leading to a greater deposition of adipose-tissue triglycerides than do isoenergetic diets with less fat. This possibility was examined by a retrospective analysis of the energy needs of 16 human subjects (13 adults, 3 children) fed liquid diets of precisely known composition with widely varied fat content, for 15-56 d (33 ± 2 d, ¯ ± SE). Subjects lived in a metabolic ward and received fluid formulas with different fat and carbohydrate content, physical activity was kept constant, and precise data were available on energy intake and daily body weight. Isoenergetic formulas contained various percentages of carbohydrate as cerelose (low, 15%; intermediate, 40% or 45%; high, 75%, 80%, or 85%), a constant 15% of energy as protein (as milk protein), and the balance of energy as fat (as corn oil). Even with extreme changes in the fat-carbohydrate ratio (fat energy varied from 0% to 70% of total intake), there was no detectable evidence of significant variation in energy need as a function of percentage fat intake. [ABSTRACT FROM AUTHOR]

Twelve young healthy adults (five men, seven women) ingested four test meals on four occasions so we could examine the relationship between the rate of gastric emptying (GE) and the glucose response to different starchy foods. Each meal consisted of one food product containing 50 g starch: spaghetti, rice, French bread, or mashed potato. Basal and postprandial glucose and insulin responses were measured for 3 h. The foods were labeled with 3.7 MBq Tc99m-albumin and GE was studied by scintigraphy for 3 h. The rate of GE (expressed by the GE half-time) was fastest for mashed potatoes, then bread, rice, and slowest for spaghetti. Blood glucose and serum insulin responses were similar. A significant negative correlation was found between the GE half-time and the maximum variation in blood glucose level (r = -0.6, p < 0.0001). The glucose response to all four foods is strongly related to the GE rate. [ABSTRACT FROM AUTHOR]

The hypothesis that high-carbohydrate feeding leads to increased insulin secretion, sodium retention, and elevation in blood pressure was examined in seven healthy men. A baseline 7-day balance study on low (13%) or high (52%) carbohydrate was followed by a 2-wk balance on the alternate diet and a 1-wk balance on the baseline diet Results indicated that changing carbohydrate intake caused a rapid (2-3 day) inverse change in urinary sodium excretion and balance. By the second week, however, urinary-sodium level returned to baseline accompanied by an inverse change in plasma aldosterone. No significant rise in blood pressure was detected throughout the study. High-carbohydrate feeding promotes sodium retention in normal subjects, but the effect is counterregulated by a reduction in plasma aldosterone. A high-carbohydrate diet in healthy subjects does not cause a significant short-term increase in blood pressure. [ABSTRACT FROM AUTHOR]

To evaluate glucose and insulin responses after ingestion of snacks, we gave healthy, nondiabetic male subjects carbohydrate equivalent (25 g) snacks or isocaloric (265 kcal) snack meals in a random crossover design. Individual snacks composed of either a milk chocolate bar, granola bar, chocolate milk, peanut butter cups, yogurt, or potato chips produced similar glucose response curves. Plasma glucose concentrations were lower (p ≤ 0.05) at 30 and 60 mm postprandially than after a corresponding oral glucose challenge. In contrast, insulin responses to the snacks exhibited a two-fold variation in peak values. Isocaloric snack meals of cereal-milk, cheese sandwich-milk, and peanut butter sandwich-chocolate milk produced glucose and insulin responses similar to individual snacks. Although glucose concentrations at 60 mm fell somewhat below baseline values after each snack, clinical hypoglycemia was not evident These data clearly indicate a similarity in glycemic response among normal individuals consuming a variety of common snacks. [ABSTRACT FROM AUTHOR]

The effect of a 50 g starch meal prepared with pre-cooked instant bean flakes on glucose and insulin plasma levels and on glucose oxidation rate as measured by continuous indirect calorimetry was assessed in six healthy human volunteers during 4 h following the meal. Comparison was done with the same load of starch as potato flakes to which the fiber and protein content of the bean meal had been added. Thirty minutes after ingestion, plasma glucose and insulin rise was less after beans than after potatoes (0.4 ± 0.2 vs 2.0 ± 0.3 mmol · l-1 ± p < 0.01 and 8 ± 2 vs 38 5 µU · ml-1 p < 0.001). The elevation of glucose oxidation was markedly less during the 2 h following the ingestion of beans when compared to potatoes. The bean flakes meal gave rise to only moderate elevation of plasma glucose and insulin levels and of glucose oxidation rate when given to four non-insulin-dependent-diabetes mellitus patients. It is suggested that the slow carbohydrate property of legumes is not due to their fiber content, but might be related to the histological structure of the seed. [ABSTRACT FROM AUTHOR]