CURRENT SCIENCE
CURRENT SCIENCE
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Energy-balance studies reveal associations between gut microbes, caloric load, and nutrient absorption in humans.
Recent studies in mice have indicated an interrelation between energy balance, diet, and the composition of the gut bacteria. So that a diet known to cause weight gain in mice was fed to mice in a germ-free environment or with normal bacteria in the colon. The mice with bacteria had greater weight gain than the mice living in a germ-free environment, suggesting that the bacteria increased efficiency with which calories from the food were absorbed into the body compared to mice that were germ-free eating the same foods. Investigators in this clinical study tested how gut bacteria were affected by changing the number of calories eaten of a constant diet by 12 lean and 9 obese men from a weight-maintaining diet to 2,400 to 3,400 calories per day.
The main point was to see whether the gut bacteria affected the efficiency of retaining calories in the body from the foods eaten. All diets had a similar composition (24% protein, 16% fat, and 60% carbohydrates) and fiber content. They found that changing diet resulted in changes in the amount of energy absorbed by about 150 calories and these changes were associated with a 20% increase in the population of a bacterial species called Firmicutes, while at the same time there was a decrease in another bacterial species, Bacteroides. These results show that overfeeding calorie can influence the gut bacterial structure over short time periods and affect energy balance.
Jumpertz R, Le DS, Turnbaugh PJ, Trinidad C, Bogardus C, Gordon JI, Krakoff J. Am J Clin Nutr. 2011; 94:58-65.
J. Nutr. 2011;141 249-254
http://www.ajcn.org/content/94/1/58.abstract -
Effect of proteins from different sources on body composition.
High-protein diets have beneficial effects on body fat regulation, but the difference in effect of various types of protein is not known. Thus, this review examines whether proteins from different sources have similar effects on body composition and energy balance. Animal proteins, especially those from dairy, seem to support better muscle protein synthesis than plant proteins. This could potentially enhance energy expenditure, but no conclusion can be drawn from the scant evidence. Some studies, but not all, demonstrate the higher satiating effect of whey and fish proteins than other protein sources. The evidence from intervention studies comparing the effects of different protein sources on body weight is inconclusive. However, body composition was not evaluated precisely in these studies and the literature is still incomplete (e.g. comparative data are missing for legumes and nuts). Protein intake enhances energy expenditure, satiety and fat loss, but there is no clear evidence to indicate whether there is a difference in the effect dependent on the source of the protein, i.e. from animal or plant-based foods.
Gilbert JA, Bendsen NT, Tremblay A, Astrup A.
Nutr Metab Cardiovasc Dis. 2011 May 10. [Epub ahead of print] PubMed PMID: 21565478.
http://www.sciencedirect.com/science/article/pii/S0939475311000020 -
Changes in Diet and Lifestyle, and Long-Term Weight Gain in Women and Men.
This study analyzed data from three very large groups of subjects who completed questionnaires between 1986 and 2006, including 120,877 healthy non-obese U.S. women and men. The relationships between changes in lifestyle factors and weight change were evaluated at 4-year intervals. Within each 4-year period, subjects gained an average of 3.35 lb. The 4-year weight change was most strongly associated with the intake of potato chips (1.69 lb), potatoes (1.28 lb), sugar-sweetened beverages (1.00 lb), unprocessed red meats (0.95 lb), and processed meats (0.93 lb); and was inversely associated with the intake of vegetables (−0.22 lb), whole grains (−0.37 lb), fruits (−0.49 lb), nuts (−0.57 lb), and yogurt (−0.82 lb) (P≤0.005 for each comparison). Specific dietary and lifestyle factors are independently associated with long-term weight gain, with a substantial aggregate effect and implications for strategies to prevent obesity.
Mozaffarian D, Hao T, Rimm EB, Willett WC, Hu FB.
N Engl J Med. 2011 Jun 23;364(25):2392-404.
http://www.nejm.org/doi/full/10.1056/NEJMoa1014296 -
Fat distribution in men of different waist girth, fitness level and exercise habit.
The risk of chronic disease is lower in obese men who are fit and active than obese men who are unfit and inactive. MRI was used to assess total and regional adipose tissue in 13 men who were slim, fit and active (the slim-fit), in 12 men who were slim, unfit and inactive (the slim-unfit), in 13 men who were fat, fit and active (the fat-fit), and in 12 men who were fat, unfit and inactive (the fat-unfit). Waist girth was used to distinguish slim men (< or =90 cm) and fat men (> or =100 cm). Maximal oxygen consumption was used to identify fit men (above average for age) and unfit men (average or below for age). Fit men reported at least 60 min of vigorous aerobic activity per week and unfit men reported no regular moderate or vigorous activity in the last 2 years.
Total fat was not significantly different from the slim-fit to the slim unfit, but the proportion of internal fat was significantly lower (P<0.05) and the proportion of visceral fat trended lower (P=0.06) in the slim-fit than all other groups.
Total fat was not significantly different in the fat-fit and the fat-unfit, but visceral fat and liver fat were significantly lower in the fat-fit than the fat-unfit (P<0.01). Waist girth and years of exercise explained 84% of the variance in total fat, waist girth and maximal oxygen consumption explained 70% of the variance in visceral fat, and waist girth alone explained 25% of the variance in liver fat. Chronic disease risk may be lower because visceral fat and liver fat are lower in men who are fat, fit and active.
O'Donovan G, Thomas EL, McCarthy JP, Fitzpatrick J, Durighel G, Mehta S, Morin SX, Goldstone AP, Bell JD.
Int J Obes. 2009; 33:1356-62.
http://www.ncbi.nlm.nih.gov/pubmed/19752873 -
Higher Branched-Chain Amino Acid Intake Is Associated With a Lower Prevalence of Being Overweight or Obese in Middle-Aged East Asian and Western Adults.
Branched-chain amino acids (BCAA), provided as a supplement, have been shown in animal and human studies to have beneficial effects on body weight. This study examined the relationship between BCAA intake and the risk of overweight and obesity among a cross-sectional cohort of over 4,000 adults in China, Japan, the United Kingdom and the United States, and found that a higher dietary intake of BCAA is associated with a lower prevalence of overweight and obesity.
Li-Qiang Qin, Pengcheng Xun, Deborah Bujnowski, Martha L. Daviglus, Linda Van Horn, Jeremiah Stamler, Ka He, and for the INTERMAP Cooperative Research Group
J. Nutr. 2011;141 249-254
http://jn.nutrition.org/cgi/content/abstract/141/2/249 -
Food Prices Are Associated With Dietary Quality, Fast Food Consumption, and Body Mass Index among U.S. Children and Adolescents.
Using nationwide data from U.S. studies, surveys of 6,759 children and 1,679 adolescents on food intake, dietary intake, body mass index (BMI) and price indexes, the purpose of this study was to examine associations of the prices of fast foods (FF), and fruits and vegetables (FV) with dietary quality and BMI. Among children aged 2 to 9 years, a higher price index for FF was associated with less FF intake, and higher intakes of fiber, calcium, dairy and FV and overall better diet quality. An increased price index for FV was associated with lower fiber intake and higher BMI, while findings among adolescents were less consistent.
May A. Beydoun, Lisa M. Powell, Xiaoli Chen, and Youfa Wang
J. Nutr. 2011;141 304-311
http://jn.nutrition.org/cgi/content/abstract/141/2/304 -
Exercising Before Protein Intake Allows for Greater Use of Dietary Protein–Derived Amino Acids for de Novo Muscle Protein Synthesis in Both Young and Elderly Men.
In young adults, muscle protein synthesis is responsive to diet and exercise, but this response appears to be blunted in the elderly, which can lead to the loss of skeletal-muscle mass (sarcopenia). Protein digestion and absorption, and subsequent muscle protein synthesis, were examined in both young and elderly men who consumed 20 g of protein both at rest and after exercise. Protein digestion and absorption were not impaired after exercise among the elderly subjects, and protein intake after exercise allowed for greater muscle synthesis in men in both age groups.
Bart Pennings, René Koopman, Milou Beelen, Joan MG Senden, Wim HM Saris, and Luc JC van Loon
Am J Clin Nutr 2011;93 322-331
http://www.ajcn.org/cgi/content/abstract/93/2/322 -
Social Influences Are Associated With BMI and Weight Loss Intentions in Young Adults.
In the United States, forty percent of young adults, aged 18 to 25 years, are overweight or obese (OW/OB), and experience the greatest rate of weight gain. This study examined the effects of social influence on weight and intentions for weight control and found that among OW/OB subjects, having more social contacts trying to lose weight, and having greater social norms for weight loss were correlated with greater intention to lose weight.
Leahey TM, Larose JG, Fava JL, Wing RR. Obesity (Silver Spring). 2010 Dec 16. [Epub ahead of print]
http://www.ncbi.nlm.nih.gov/pubmed/21164501 -
Dietary Inorganic Nitrate Improves Mitochondrial Efficiency in Humans.
Nitrate is naturally present in vegetables, and is converted in the body to various compounds, including nitric oxide. In this study, subjects were given nitrate supplements, in an amount similar to what would be found in 2 to 3 beets or a plate of spinach, for three days, and its effects on energy production in skeletal muscle and whole-body oxygen consumption during exercise, were studied. After nitrate supplementation, subjects consumed less oxygen while exercising, which was correlated with improved efficiency of skeletal muscle mitochondria that power cells.
Larsen FJ, Schiffer TA, Borniquel S, Sahlin K, Ekblom B, Lundberg JO, Weitzberg E.
Cell Metab. 2011 Feb 2;13(2):149-59.
http://www.ncbi.nlm.nih.gov/pubmed/21284982
