The energy values of carbohydrates continue to be debated. This is because of the use of different energy systems, for example, combustible, digestible, metabolizable, and so on. Furthermore, ingested macronutrients may not be fully available to tissues, and the tissues themselves may not be able fully to oxidize substrates made available to them. Therefore, for certain carbohydrates, the discrepancies between combustible energy (cEI), digestible energy (DE), metabolizable energy (ME) and net metabolizable energy (NME) may be considerable. Three food energy systems are in use in food tables and for food labelling in different world regions based on selective interpretation of the digestive physiology and metabolism of food carbohydrates. This is clearly unsatisfactory and confusing to the consumer. While it has been suggested that an enormous amount of work would have to be undertaken to change the current ME system into an NME system, the additional changes may not be as great as anticipated. In experimental work, carbohydrate is high in the macronutrient hierarchy of satiation. However, studies of eating behaviour indicate that it does not unconditionally depend on the oxidation of one nutrient, and argue against the operation of a simple carbohydrate oxidation or storage model of feeding behaviour to the exclusion of other macronutrients. The site, rate and extent of carbohydrate digestion in, and absorption from the gut are key to understanding the many roles of carbohydrate, although the concept of digestibility has different meanings. Within the nutrition community, the characteristic patterns of digestion that occur in the small (upper) vs large (lower) bowel are known to impact in contrasting ways on metabolism, while in the discussion of the energy value of foods, digestibility is defined as the proportion of combustible energy that is absorbed over the entire length of the gastrointestinal tract. Carbohydrates that reach the large bowel are fermented to short-chain fatty acids. The exact amounts and types of carbohydrate that reach the caecum are unknown, but are probably between 20 and 40 g/day in countries with 'westernized' diets, whereas they may reach 50 g/day where traditional staples are largely cereal or diets are high in fruit and vegetables. Non-starch polysaccharides clearly affect bowel habit and so, to a lesser extent, does resistant starch. However, the short-chain carbohydrates, which are also found in breast milk, have little if any laxative role, although do effect the balance of the flora. This latter property has led to the term 'prebiotic', which is defined as the capacity to increase selectively the numbers of bifidobacteria and lactobacilli without growth of other genera. This now well-established physiological property has not so far led through to clear health benefits, but current studies are focused on their potential to prevent diarrhoeal illnesses, improve well-being and immunomodulation, particularly in atopic children and on increased calcium absorption.

Physiological aspects of energy metabolism and gastrointestinal effects of carbohydrates.

Substituting whole grains for refined grains in a 6-wk randomized trial favorably affects energy-balance metrics in healthy men and postmenopausal women.

The present review considers the background to terminology that relates foods, glycaemia and health, including ‘available carbohydrate’, ‘glycaemic index’ (GI), ‘glycaemic glucose equivalent’, ‘glycaemic response index’ and ‘net carbohydrate’, and concludes that central to each of these terms is ‘glycaemic load’ (GL). GL represents the acute increase in exposure of tissue to glucose determined by foods; it is expressed in ingested glucose equivalents (per 100 g fresh weight or per serving), and is regarded as independent of the state of glucose metabolism from normal to type 2 diabetes mellitus (T2DM). Ad libitum studies in overweight or obese adults and children show that low-GL diets are associated with marked weight benefits, loss of adiposity and reduced food intake. Weight benefits appear on low-glycaemic v. high-glycaemic available carbohydrates, unavailable v. available carbohydrates and protein v. available carbohydrate. Energy intake immediately after lowering of meal GL via carbohydrate exchanges is apparent only after a threshold cumulative intake of >2000 MJ. Various epidemiological and interventional studies are discussed. A relationship between GL and the development of T2DM and CHD is evident. Studies that at first seem conflicting are actually consistent when data are overlaid, such that diets with a GL of >120 glucose equivalents/d would appear to be inadvisable. Whereas certain studies might place GI as being slightly stronger than GL in relation to T2DM risk, this situation appears to be associated with observations in a lower range of GL or when the range of GI is too narrow for accuracy; nevertheless, authors emphasise the importance of GL. Among the studies reviewed, GL offers a better or stronger explanation than GI in various observations including body weight, T2DM in nurses, CHD, plasma triacylglycerols, HDL-cholesterol, high-sensitivity C-reactive protein and protein glycation. Where information is available, the associations between risk factors and GL are either similar or stronger in the overweight or obese, as judged by BMI, and apply to both body weight and blood risk factors. The implications tend to favour a long-term benefit of reducing GL, for which further study is necessary to eliminate any possibility of publication bias and to establish results in clinical trials with overweight and obese patients. Obesity: Diabetes: CHD: Health markers: Glycaemic load

/pdf/low-glycaemic-diets-and-health-implications-for-obesity-tjc0ok6f2r.pdf

Low-glycaemic diets and health: implications for obesity

Accuracy of the Atwater factors and related food energy conversion factors with low-fat, high-fiber diets when energy intake is reduced spontaneously

In the last several decades, obesity rates have reached epidemic proportions, and increases the risk for a host of comorbidities, including diabetes, cardiovascular disease, and certain kinds of cancers. Boba milk tea, first became popular in the 1990s throughout Asia, and has gained more popularity in the United States and in Europe since 2000. Currently, available nutrition data from online sites suggest this beverage contains high amounts of sugar and fat. One published nutrition study suggests that boba tea drinks are part of the larger group of sugar-sweetened beverages (SSB) because these beverages are usually sweetened with high-fructose corn syrup (HFCS). This study experimentally determined the sugar composition (sucrose, fructose, glucose, and melezitose) and calorific values of boba milk tea drinks and their components. Results suggested that boba drinks fit the US Dietary Guidelines definition of a SSB. One 16-ounce boba drink exceeds the upper limit of added sugar intake recommended by the 2015 US Dietary Guidelines Advisory Committee. The high caloric and sugar content of boba beverages pose public health concerns as they have the potential to further exacerbate the childhood obesity epidemic. Nutrition education targeting Asian populations should give special attention to boba tea as a SSB. Also, prudent public health recommendations should be suggested for moderate consumption of these beverages. With the growing popularity of boba beverages in the United States, the findings from this study provide public health practitioners with valuable data on how boba beverages compare with other SSBs.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/fsn3.362

Calories and sugars in boba milk tea: implications for obesity risk in Asian Pacific Islanders.

BACKGROUND: Animal studies and theory show fermentable carbohydrate (FC) intake causes appreciably thermogenesis, but a similar occurrence in humans is controversial. HYPOTHESES: (a) That indirect calorimetry (IDC) is a valid method to assess thermogenesis during fermentation. (b) That a consistent and rigorous approach to the analysis of published IDC data from human studies will establish a representative thermogenic response to FC. (c) That conventional estimates of food energy and energy requirements can mismatch appreciably, more especially when thermogenesis is ignored. PURPOSE: To derive information and understanding of IDC, thermogenesis and energy balance in relation to food energy and energy requirement estimates. METHODS: (a) The validities of IDC equations that estimate the heat of reaction and carbohydrate utilization were assessed for various types of FCs under various circumstances. (b) Pooled analysis of eight published randomized cross-over studies in humans with elevation of FC intake. Studies were analysed for the first time or reanalysed according to a consistent approach with appropriate corrections for confounders. (c) Some 1500 regular and ‘special’ diet compositions were examined to assess the extent to which Atwater general food energy factors and updated estimates of energy requirements mismatch due to variation in substrate-associated thermogenesis and substrate-associated faecal+urinary energy losses. Impact of such mismatches on BMI was assessed under conditions of all else being equal. RESULTS: (a) Indirect calorimetry was valid, providing robust estimates of heat production during various types of fermentation; only small correction factors were necessary. By contrast, IDC equations for carbohydrate utilization sometimes applied poorly to FC. (b) A best estimate of thermogenesis in humans due to fermentation, above that due to oral glucose as a reference standard, was 0.39 (s.e.m. 0.14) kJ per kJ net metabolizable energy (NME; P<0.05, n=8 studies, total 72 humans) compared with 0.34 kJ/kJ from theory. Six sources of bias were identified; all had potential to underestimate FC thermogenesis. (c) Mismatches in energy availability and requirement estimates were often marked and translated into long-term differences in body mass index from ∼20 to 33 kg/m2 in average-height middle-aged initially obese women, and from ∼22 to a non-survivable 13 kg/m2 in initially slim women. CONCLUSIONS: (a) Indirect calorimetry is valid for the present purpose. (b) Thermogenesis in response to FC is real in humans and is comparable to that in animals and in theory. (c) Mismatches between estimates of energy requirements and dietary energy as metabolizable energy means the two expressions are not directly comparable, which has implications for the expression of food energy, energy requirements and the conduct and interpretation of research related to body weight.

Thermogenesis associated with fermentable carbohydrate in humans, validity of indirect calorimetry, and implications of dietary thermogenesis for energy requirements, food energy and body weight.

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Thermogenesis associated with fermentable carbohydrate in humans, validity of indirect calorimetry, and implications of dietary thermogenesis for energy requirements, food energy and body weight.