Is a Calorie Really a Calorie? Metabolic Advantage of Low-Carbohydrate Diets

The first law of thermodynamics dictates that body mass remains constant when caloric intake equals caloric expenditure. It should be noted, however, that different diets lead to different biochemical pathways that are not equivalent when correctly compared through the laws of thermodynamics. It is inappropriate to assume that the only thing that counts in terms of food consumption and energy balance is the intake of dietary calories and weight storage. Well-controlled studies suggest that calorie content may not be as predictive of fat loss as is reduced carbohydrate consumption. Biologically speaking, a calorie is certainly not a calorie. The ideal weight loss diet, if it even exists, remains to be determined, but a high-carbohydrate/low-protein diet may be unsatisfactory for many obese individuals.     

World need for protein

On the basis of the 1973 FAO/WHO recommendations for average calorie requirements and safe protein allowances for healthy individuals, both calorie and protein intakes are generally deficient in the lower socioeconomic groups of developing countries, with calories apparently the more limiting in most cases. However, extensive data available since 1973 indicate that the 1973 protein allowances for healthy adults approximated the mean rather than the mean plus two standard deviations as intended. For those individuals in developing countries who are frequently unhealthy, requirements may be even higher. Children have considerably higher protein requirements for catch-up growth following episodes of acute infection; failure to obtain sufficient protein appears to be a major factor in the pemanent stunting of such children. Requirements for dietary energy increase much less for catch-up growth than requirements for protein. Comparing calorie intakes with international estimates of requirements has limited validity because of the human capacity to adjust to a decreased dietary energy intake by reducing physical activity. No comparable adaptation is known for low dietary protein intakes; instead, under the conditions responsible for limited food availability, protein requirements are likely to increase because of acute and chronic infections. Although differences in protein quality can be demonstrated by experimental animal and human studies in which protein intake is grossly deficient, little difference is detectable in studies where protein intake is at requirement levels. Thus, soy and other legume and oilseed protein sources can replace animal protein to any degree in human diets.     

Impact of fat substitutes on fat intake

Dietary fat is the number one nutrition concern of Americans. In response to rising consumer demand for reduced-fat foods, the food industry has developed a multitude of nonfat, lowfat, and reduced-fat versions of regular food products. To generate reduced-fat or fat-free products that have the same organoleptic characteristics of the regular fat version, food manufactures frequently employ fat substitutes in the formulation of these foods. Fat substitutes are made from either carbohydrate, protein, or fat, or a combination of these components. Researchers have questioned the impact of fat substitutes on both fat and caloric intake. The majority of research studies in which fat substitutes were either covertly or overtly substituted for dietary fat indicate that in short-term, carefully-controlled conditions, fat substitutes can decrease both dietary fat intake and percentage of calorie intake from fat. However, individuals compensate for the caloric deficit created by the fat substitutes by increasing their consumption of other macronutrients, primarily carbohydrate. The long-term effect of fat substitutes on the fat intake of free-living individuals and weight control are unknown. People tend to eat more of a food when they know that food is reduced in fat. Fat substitutes should not be considered a substitute for sound nutrition education and a healthy lifestyle which includes regular exercise.     

Carbohydrates and fiber

Dietary carbohydrates comprise two fractions that may be classified as digestible, and which are useful as energy sources (simple and complex carbohydrates) and fiber, which is presumed to be of no use to the human body. There are insufficient epidemiologic data on the metabolic effects of simple carbohydrates and it is not advisable to make quantitative recommendations of intake. It is questionable to recommend in developing countries that a fixed proportion of dietary energy be derived from simple sugars, due to the high prevalence of deficient energy intake, cultural habits, and regional differences in food intake and physical activity. In relation to recommendations of complex carbohydrates, it should be considered that their absorption is influenced by many factors inherent to the individual and to the foods. Fiber is defined as a series of different substances derived from tissue structures, cellular residues and undigested chemical substances that may be partially utilized after intestinal bacteria have acted on them. There is not a clear definition of the chemical composition of fiber, but it consists mainly of polysaccharides (such as cellulose, hemicellulose and pectins), lignin and end products of the interactions of various food components. The effects of fiber, such as control of food intake, regulation of gastrointestinal transit, post-prandial blood concentrations of cholesterol, glucose and insulin, flatulence and alterations in nutrient bioavailability are due to various physical properties inherent to its chemical components. Impairment of nutrient absorption may be harmful, mainly among populations whose food intake is lower than their energy needs, and with a high fiber content. This may be particularly important in pregnant women, growing children and the elderly, and should be considered when making nutrient recommendations. A precise knowledge of fiber is also important to calculate the real energy value of foods, mainly for two reasons: 1) the proportion of "crude fiber" (as measured by acid and alkaline digestion) leads to an over-estimation of the proportion of digestible carbohydrates calculated by difference; 2) fiber may alter the polysaccharide utilization of some foods, as shown by the "glycemic index". It is difficult to make recommendations on dietary fiber due to insufficient data on intake, fiber composition, its physiological effects, and epidemiological studies. However, a preliminary evaluation of the diets from most Latin American countries shows large intakes of vegetable foods and, consequently, an adequate fiber intake may be expected.     

International Society of Sports Nutrition position stand: energy drinks

Position Statement: The International Society of Sports Nutrition (ISSN) bases the following position stand on a critical analysis of the literature on the safety and efficacy of the use of energy drinks (ED) or energy shots (ES). The ISSN has concluded the following. 1. Although ED and ES contain a number of nutrients that are purported to affect mental and/or physical performance, the primary ergogenic nutrients in most ED and ES appear to be carbohydrate and/or caffeine. 2. The ergogenic value of caffeine on mental and physical performance has been well-established but the potential additive benefits of other nutrients contained in ED and ES remains to be determined. 3. Consuming ED 10-60 minutes before exercise can improve mental focus, alertness, anaerobic performance, and/or endurance performance. 4. Many ED and ES contain numerous ingredients; these products in particular merit further study to demonstrate their safety and potential effects on physical and mental performance. 5. There is some limited evidence that consumption of low-calorie ED during training and/or weight loss trials may provide ergogenic benefit and/or promote a small amount of additional fat loss. However, ingestion of higher calorie ED may promote weight gain if the energy intake from consumption of ED is not carefully considered as part of the total daily energy intake. 6. Athletes should consider the impact of ingesting high glycemic load carbohydrates on metabolic health, blood glucose and insulin levels, as well as the effects of caffeine and other stimulants on motor skill performance. 7. Children and adolescents should only consider use of ED or ES with parental approval after consideration of the amount of carbohydrate, caffeine, and other nutrients contained in the ED or ES and a thorough understanding of the potential side effects. 8. Indiscriminant use of ED or ES, especially if more than one serving per day is consumed, may lead to adverse events and harmful side effects. 9. Diabetics and individuals with pre-existing cardiovascular, metabolic, hepatorenal, and neurologic disease who are taking medications that may be affected by high glycemic load foods, caffeine, and/or other stimulants should avoid use of ED and/or ES unless approved by their physician.     

Macronutrient profile affects diet-induced thermogenesis and energy intake

The diet composition can interfere directly in the energy homeostase. In the energy metabolism, the oxidation pathway and diet-induced thermogenesis are differentiated by diet macronutrients proportion. In this respect, the high-protein diet is the most thermogenic, compared to high-carbohydrate and high-lipid diets, while high-carbohydrate diet appears to increase the thermogenic effect more than high-lipid diet, but the studies are controversies. Towards energy intake, it can stimulate or inhibit the energy intake, according to the foods palatability, satiation and satiety degree, related to diet carbohydrate, protein and lipid content. A hierarchy has been observed for the satiating efficacies of the macronutrients protein, carbohydrate and fat, with protein as most satiating and fat as least satiating. In general, there are discrepancies between studies about the regulatory role of macronutrients in the components of energy expenditure and intake, due the methodological differences in the subjects, exposition time for diet, energy density, and total energy content. The present work seeks to analyze the more consistent scientific evidences toward the modulator role of diet composition on the diet induced thermogenesis and energy intake, for better understanding of obesity prevention and control by dietetic intervention.     

The management of obesity

The prevalence and incidence of obesity is rising as current ways of managing obesity are proving to be ineffective. The preferred approach is to induce an energy deficit by decreasing energy intake through a low calorie diet and increasing energy expenditure through exercise. In order to provoke body weight loss the changes in lifestyle that this approach involves have to be sustained and while some individuals have the motivation to do this the vast majority of the population has not. Very low calorie diets are ineffective as the body adapts to them by lowering energy expenditure and altering the macronutrient composition of low calorie diets has no additional effect. The anti‐obesity drugs orlistat, sibutramine and rimonabant can provoke body weight loss but all suffer from side effects. However, the explosion in our understanding of the factors that regulate energy intake is likely to lead to the development of more effective drugs with fewer side effects. Bariatric or weight reducing surgery is highly effective at provoking body weight loss but there are obvious barriers to its widespread use.     

Fats in indian diets and their nutritional and health implications

To arrive at fat requirements for Indians; the contribution of invisible fat should be determined. Total lipids were extracted from common Indian foods, and their fatty acid compositions were determined. This data and information on intake of various foods were used to estimate the contents of “invisible” fat and fatty acids in Indian diets. Taking into account World Health Organization (WHO) guidelines and the invisible-fat intake of Indians, recommendations were made for lower and upper limits of visible fats. In the rural poor, the “visible”-fat intakes are much lower than estimated minimum requirements. Therefore, to meet the energy needs of low-income groups, particularly young children, visible-fat intakes must be increased to recommended levels. The urban high-income group, however, should reduce dietary fat. Data on intake of various fatty acids in total diet shows that even the recommended lower limit of oil can meet linoleic acid requirements. Intake of α-linolenic acid is low, however. Increase in dietary n-3 polyunsaturated fatty acid (PUFA) produces hypolipidemic, anti-inflammatory, and antithrombotic effects. Effects of n-3 PUFA on blood lipids, platelet fatty acid composition, and platelet aggregation were therefore investigated in Indian subjects consuming cereal-based diets. Supplementation of fish oils (long-chain n-3 PUFA) as well as the use of rapeseed oil (α-linolenic acid) produced beneficial effects. Since the requirements of α-linolenic acid and/or long-chain n-3 PUFA are related to linoleic acid intake, use of more than one oil (correct choice) is recommended for providing a balanced intake of various fatty acids. Analysis of Indian food showed that some foods are good sources of α-linolenic acid. Regular consumption of these foods can also improve the quality of fat in Indian diets. Nonvegetarians, however, have the choice of eating fish to accomplish this.     

No evidence of differential effects of SFA,MUFA or PUFA on post-ingestive satiety and energy intake: a randomised trial of fatty acid saturation

Background  

High fat diets have long been associated with weight gain and obesity, and the weak satiety response elicited in response to dietary lipids is likely to play a role. Suppression of appetite and food intake has consistently been shown to be diminished with high fat relative to either high protein or carbohydrate meals. There is however some evidence that the satiating capacity of lipids may be modulated when physicochemical properties are altered, but studies investigating the effect of lipid saturation on appetite have generated inconsistent findings. This study investigated the effects of changes in fatty acid saturation on post-ingestive satiety and energy intake.     

Dietary Lipid Intake only Partially Influences Variance in Serum Phospholipid Fatty Acid Composition in Adolescents: Impact of Other Dietary Factors

The present study aimed to assess the correlation between food and fatty acid (FA) intake and the serum phospholipid (PL) FA status in European adolescents and explored the percentage of variation in serum PL FA that could be attributed to dietary habits. Participants included 528 adolescents recruited in the HELENA Study. Dietary intake was assessed by two, self-administered, non-consecutive 24-h recalls. PL FA concentrations were measured in fasting venous serum samples. Reduced rank regressions were applied to examine the combined effect of food intakes. Results indicated that the variance in serum PL FA in adolescents, that could be explained by diet varied from 7.0 % for MUFA to 14.2 % for n-3FA. The variance in the long-chain n-3FA was mainly explained by fish intake but also by coffee and tea consumption. In conclusion this study indicated that dietary intake influences the serum PL FA status to a limited amount but that also other factors interfere. However, dietary intake is important as it is among those factors that could be modified. Furthermore, the results suggest that the overall dietary habits should be considered instead of only the consumption of single foods or nutrients, as the medium of the food or concomitant intake of foods and nutrients might interact and as such influence absorption or metabolism.     

Food deprivation affects preference of sheep for foods varying in nutrients and a toxin

We investigated how food deprivation affected preference of lambs for foods that varied in concentrations of nutrients and a toxin. Thirty lambs (10 lambs/treatment) were fed different amounts of alfalfa pellets (high in protein, marginal in energy for growth) as a basal ration (20, 40, or 60 g/kg body weight). Every morning, prior to ingesting the basal ration of alfalfa pellets, each lamb was offerend three foods for 15 min. The foods contained different amounts of energy and a toxin, depending on the addition of barley (energy) and LiCl (toxin) to alfalfa. The proportions of barley and LiCl changed every five days during the 25-day study. The results showed: (1) all lambs preferred food that was high > intermediate > low in energy (barley) in the absence of LiCl, but all lambs decreased consumption of foods high in energy as LiCl concentrations increased; (2) the greater the level of food deprivation, the lower the consumption of foods containing LiCl, even if the foods provided high levels of energy; (3) lambs moderately food deprived or fed ad libitum ingested more LiCl than lambs that were highly deprived; and (4) lambs quickly (15 min/day) regulated intake of foods in response to changes in barley and LiCl concentrations. Thus, our results suggest that the interaction between nutritional status and toxicosis plays an important role in food preference of lambs. Our findings also suggest that toxic plants may kill herbivores that lack nutritious alternative foods not only because the animals are forced to be less discriminating, but also because they are more susceptible to toxins.     

Dietary trans fatty acids: Review of recent human studies and food industry responses

Dietary trans FA at sufficiently high levels have been found to increase low density lipoprotein (LDL)-cholesterol and decrease high density lipoprotein (HDL)-cholesterol (and thus to increase the ratio of LDL-cholesterol/HDL-cholesterol) compared with diets high in cis monounsaturated FA or PUFA. The dietary levels of trans FA at which these effects are easily measured are around 4% of energy or higher to increase LDL-cholesterol and around 5 to 6% of energy or higher to decrease HDL-cholesterol, compared with essentially trans-free control diets. Very limited data at lower levels of intake (less than 4% of energy) are available. Most health professional organizations and some govemments now recommend reduced consumption of foods containing trans FA, and effective January 1, 2006, the U.S. Food and Drug Administration requires the labeling of the amounts of trans FA fer serving in packaged foods. In response, the food industry is working on ways to eliminate or greatly reduce trans FA in food products. Current efforts focus on four technological options: (i) modification of the hydrogenation process, (ii) use of interesterification, (iii) use of fractions high in solids from natural oils, and (iv) use of trait-enhanced oils. Challenges to the food industry in replacing trans FA in foods are to develop formulation options that provide equivalent functionality, are economically feasible, and do not greatly increase saturated FA content.     

Dietary fat and body weight control

The global obesity epidemic has heightened the debate about dietary factors contributing to weight gain. Media stories have promulgated the notion that obesity has increased despite reductions in dietary fat intake. Some have even speculated that lower dietary fat levels may be driving the rapid rise in weight gain within the population. A close examination of the science reveals a different picture and supports the hypothesis that dietary fat, within the context of the total dietary composition consumed by many populations, promotes obesity. Hence, dietary fat control is still an important strategy as part of an overall approach to body weight management in our modern environment. Dietary fat increases the energy density of foods. Abundant evidence from preclinical and clinical studies indicates that fat promotes excess energy intake and positive energy balance. Dietary fat does not promote its own oxidation in the body and is stored efficiently, promoting a positive fat balance. Thus, both the behavioral and metabolic responses to dietary fat increase the probability of positive energy balance and body fat gain. Restoring fat balance when consuming diets rich in fat requires increasing the size of the body fat mass, increasing physical activity, or reducing dietary fat intake. Numerous epidemiologic, preclinical, and controlled clinical studies have shown that body fat is positively associated with dietary fat intake and that dietary fat manipulation leads to appropriate changes in body fat mass. Finally, data from the National Weight Control Registry, a database of >3000 individuals who have successfully maintained a substantial weight loss, indicate that moderating dietary fat intake is a key strategy for long-term management of body weight.     

"A calorie is a calorie" violates the second law of thermodynamics

The principle of "a calorie is a calorie," that weight change in hypocaloric diets is independent of macronutrient composition, is widely held in the popular and technical literature, and is frequently justified by appeal to the laws of thermodynamics. We review here some aspects of thermodynamics that bear on weight loss and the effect of macronutrient composition. The focus is the so-called metabolic advantage in low-carbohydrate diets – greater weight loss compared to isocaloric diets of different composition. Two laws of thermodynamics are relevant to the systems considered in nutrition and, whereas the first law is a conservation (of energy) law, the second is a dissipation law: something (negative entropy) is lost and therefore balance is not to be expected in diet interventions. Here, we propose that a misunderstanding of the second law accounts for the controversy about the role of macronutrient effect on weight loss and we review some aspects of elementary thermodynamics. We use data in the literature to show that thermogenesis is sufficient to predict metabolic advantage. Whereas homeostasis ensures balance under many conditions, as a general principle, "a calorie is a calorie" violates the second law of thermodynamics.     

Role of Toxins in Intake of Varied Diets by Sheep

Herbivores foraging on toxic plants may consume a variety of foods that contain different toxins to increase food intake and to avoid toxicosis. We studied whether lambs offered two foods, each containing a different toxin, could ingest more food than lambs offered one food with a single toxin. Thirty-two lambs were allotted to four groups that received: (1) a ration with toxin A, (2) a ration with toxin B, (3) two rations, one with toxin A and the other with toxin B, and (4) a ration with no toxins. Toxin pairs used in the study were (1) amygdalin and lithium chloride (LiCl), (2) LiCl and LiCl, (3) sparteine and saponin, (4) oxalate and nitrate, and (5) tannin and saponin. For an hour each morning, lambs were offered their ration(s) and intakes were measured. Lambs were maintained on an alfalfa pellet or grass hay diet. Each trial lasted either five or six days. Whether or not lambs ate more when offered foods with different toxins depended on the kind and amount of toxin in the food. Lambs offered rations with amygdalin and LiCl or oxalate and nitrate consumed more food than lambs offered a ration with only one of these toxins. Lambs offered rations with sparteine and saponin or tannin and saponin did not eat more food than lambs offered a ration with either saponin or sparteine or tannin alone. Nor did lambs eat more when offered two rations both containing LiCl. In all trials, lambs offered toxins showed no signs of toxicosis, and they ate less food than lambs offered rations without toxins. Our results indicate that in some cases ruminants can increase intake of toxic foods by consuming foods containing different toxins. However, currently the only way to determine how specific toxins may interact in the body to influence intake would be to conduct feeding trials using plants or ground diets that contain toxins.     

Food based approaches to improve vitamin and mineral nutrition adequacy

This paper, using the nutrient density concept and the development of Food-Based Dietary Guidelines (FBDG), explores the nutritional adequacy of food patterns based on the main staples around the world--maize, wheat, rice and potato. The nutritional adequacy of the vitamins A, C, folates and the minerals iron, zinc and calcium in diets composed by these staples is analyzed. Projected diets modified by the addition of foods high in vitamins and minerals, based on food table composition information, are analyzed for changes in nutritional adequacy, in order to cover the nutritional requirements of all family members. This theoretical exercise shows that diets diversified by the addition of relatively small quantities (27-70 g) of foods like fruits, vegetables, legumes and meat improve substantially the nutritional adequacy of the vitamins A, C, folates, iron and zinc. In the case of calcium, the addition of a dairy source becomes essential. From the practical point of view, the implementation of the food based approach requires a national effort in order to support the production of nutrient rich foods and to promote consciousness of nutrient bioavailability, so that people may obtain all nutrient potential from foods. Simultaneously, the need of fortification programs at the national level is recognized. This is the case for critical nutrients, where requirements might be above the potential in available foods. A similar situation occurs in the case of vulnerable groups like pregnant women and infants, who need supplementation to ensure nutritional adequacy of their diets. In conclusion, the use of FBDG is a good alternative for improving the nutritional adequacy of diets based predominantly on staple foods. However, food fortification and supplementation programs directed to vulnerable groups are necessary and complementary practices to the FBDG implementation.     

Australian children dietary intakes with a focus on dietary fats

Australian children are consuming far too much salt and more saturated fat than the recommended intakes and this is largely due to consumption of processed foods like biscuits, cakes, pies, pizza, hamburgers, and potato chips/crisps. They consume very little in the way of vegetables and this is why magnesium and calcium intakes are low. Australian children also do not consume the beneficial omega‐3 fats which are primarily found in fish and seafood. To achieve the nutrients for optimal health Australian children should reduce their intakes of processed food and increase their intakes of wholesome foods including fish/seafood and vegetables.     

Tolerance and chronic acceptability of lupine (Lupinus albus var. Multolupa) flour for feeding of young adults

Cookies enriched with sweet lupin flour were tested for their acceptability and tolerance in young adults, and compared with control cookies. A number of hematological, hepatic and renal tests were performed, as well as the measurement of allergic response, in order to detect possible changes induced by lupin. The study included 31 young adults assigned to two groups which comprised males and females, with mean ages of 26 +/- 6.5, and 27 +/- 5.9 years, respectively. The protein and energy intakes of the subjects were calculated, prior to the study, using the methods of dietary history and the 24-hr recall method. The subjects were free of any abnormalities detectable by medical history, physical examination, biochemical and hematological tests. Body weight and height were measured before the beginning of the study. The ratio weight/height of the individuals was calculated using the Jelliffe's standards. The mean values for the calorie and protein intakes were 1,919 kcal (SD +/- 655) and 59.3 g (SD +/- 22.7). The calorie contents of the control and experimental cookies were 507 and 610 kcal respectively, while the protein contents were 8.4 g and 24.1 g, respectively. The body weight of subjects in both groups increased significantly during the study (P less than 0.01 and P less than 0.02). No significant changes were recorded for other anthropometric parameters, except for the tricipital skinfold (P less than 0.01). Changes observed in hematological parameters were judged to be unrelated to lupin flour. The acceptability and tolerance to high levels of lupin flour were good. The above-mentioned results show that sweet lupin flour is a good and safe source of energy and protein for adults.     

Improving the nutritional properties of rapessed

Canadian plant breeders have recently succeeded in producing rapeseed with <1% erucic acid in the oil and with a very low level of glucosinolates in the meal. One suchBrassica napus cultivar, ‘Tower,’ is now licensed. The meal from ‘Tower’ seed has been subjected to extensive chemical and biological testing and has proven to be a markedly superior product as compared with conventional rapeseed meals. This new cultivar is less goitrogenic and more palatable and gives satisfactory productive performance in animals at use levels well in excess of older varieties. The presence of high levels of erucic acid in older varieties made the oils undesirable, particularly because this compound is not well metabolized by cardiac and certain other tissues and results in pathological changes in a number of experimental animals. ‘Tower’ rapeseed oil is less cardiotoxic than high erucic oils and appears to be no more detrimental when used at the 20% level in animal diets than a number of other oils used in human foods.     

Saturated fat and heart disease: The latest evidence

In recent years, many nutrition news headlines exclaimed that saturated fat was not linked to heart disease, leaving the public confused about whether to limit intake, as has been the dietary recommendation for several decades. However, a more nuanced look at the evidence indicates that high saturated fat diets are in fact not benign with respect to heart disease risk. Dietary recommendations should emphasize replacing saturated fats typical in red and processed meats, and certain tropical oils and dairy forms, with healthier polyunsaturated and monounsaturated fat‐rich foods, such as nuts, olive oil, and fatty fish, as well as healthy sources of carbohydrates, such as fiber‐rich whole‐grain foods, rather than refined‐grain and sugar‐laden foods.