100+ Putative Causes Of Obesity – Take Your Pick

Listening to (or reading the bestsellers written by) pundits, one may easily think that the entire obesity problem can be brought down to a couple of factors – sugar-sweetened beverages, fast food, sedentariness, screen-time, – take your pick. Now, Morgan Downey, former CEO of the Obesity Society on his blog – the Downey Obesity Report – provides an update of previous lists of putative causes of obesity – a list that now included 104 items. As he is careful to point out, “The links are not meant to be definitive or best study but merely a demonstration of the interest in the particular cause.” Given that many of these factors are implicated based largely on observational studies, which by their very nature cannot prove causality, some scepticism is in order. However, for many factors on this list there is biological plausibility, often backed by findings from animal or experimental studies. Here is Downey’s list of putative causes of obesity: 1. agricultural policies 2. air conditioning, 3. air pollution, 4. antibiotic usage at early age, 5. arcea nut chewing, 6. artificial sweeteners, 7.  Asian tiger mosquitos, 8. assortative mating, 9. being a single mother, 10. birth by C-section, 11. built environment, 12. celebrity chefs, 13. chemical toxins, (endocrine disruptors) 14. child maltreatment, 15. compulsive buying, 16. competitive food sales in schools, 17. consuming skim milk in preschool children, 18. consumption of pastries and chocolate (in Burkina Faso), 19. decline in occupational physical activity, 20. delayed prenatal care, 21. delayed satiety, 22. depression 23. driving children to school 24. eating away from home 25. economic development (nutrition transition) 26. entering into a romantic relationship, 27. epigenetic factors, 28. eradication of Helicobacter pylori, 29. family conflict, 30. family divorce, 31. first-born in family, 32. food addiction, 33. food deserts, 34. food insecurity, 35. food marketing to  children, 36. food overproduction, 37. friends, 38. genetics, 39. gestational diabetes, 40. global food system,(international trade policies) 41. grilled foods, 42. gut microbioata, 43. having children, for women, 44.  heavy alcohol consumption, 45.  home labor saving devices, 46. hormones (insulin,glucagon,ghrelin), 47. hunger-response to food cues, 48. high fructose corn syrup, 49. interpersonal violence, 50. lack of family meals, 51. lack of nutritional education, 52. lack of self-control, 53. large portion sizes, 54.  living in crime-prone areas, 55. low educational levels for women, 56. low levels of physical activity, 57. low Vitamin D levels, 58.  low socioeconomic status, 59. market economy, 60. marrying in later life 61. maternal employment, 62. maternal obesity, 63. maternal over-nutrition during pregnancy, 64. maternal smoking, 65. meat consumption, 66. menopause, 67. mental disabilities, 68. no or short term breastfeeding, 69. non-parental childcare 70. outdoor advertising, 71. overeating, 72. participation in Supplemental Nutrition Assistance Program (formerly Food Stamp Program) 73. perceived weight discrimination, 74. perception of neighborhood safety, 75. physical disabilities, 76. prenatal  maternal exposure to natural disasters, 77. poor emotional coping 78. sleep deficits, 79. skipping… Read More »

New Year’s Resolution: Use Chop Sticks?

Just in time for the new year, a group of researchers from Singapore show that eating rice with chopsticks may reduce its glycemic index compared to using a spoon. This randomised controlled trial, published in Physiology & Behaviour, involved eleven healthy volunteers, who came in on six non-consecutive days to the laboratory and evaluated three methods of eating white rice (spoon, chopsticks and fingers) once and the reference food (glucose solution) three times in a random order. The three modes of eating were chosen to represent the most common eating habits of the various ethnic communities living in Singapore – chopsticks (Chinese), fingers (Malay and Indian) or spoon (Chinese, Malay and Indian). Based on the glycemic response (GR) over 120 mins after ingestion of each test meal, the glycemic index of eating rice with chopsticks was 68 compared to 81 when eating the same amount of rice with a spoon was measured for the subsequent 120 min (eating with fingers fell in the middle). The most likely explanation for this difference is the finding that the mode of eating significantly affected the number of mouthfuls, the number of chews per mouthful, the chewing time per mouthful, and the total time taken to consume the whole portion of rice. Not surprisingly, these parameters were significantly correlated to the glycemic response. If nothing else, this study should remind us that taking more time to eat and better chewing your food may affect the processing and metabolic response to what you eat – thus, it appears that when it comes to healthy eating – the “how” may well be as important as the “what”. @DrSharma Princeton, NJ

Hormonal Responses to Food Intake Begin in Your Mouth

In my current show at the 33rd Edmonton International Fringe Theatre Festival, I joke about the importance of chewing your food. This has classically been noted to be of importance to allow the enzymes in saliva to begin the process of digestion. However, now a fascinating study by Yong Zhu and colleagues from Iowa State University, published in Physiology and Behaviour shows that chewing prompts hormonal changes that vary based on the composition of the food. In their study, ten healthy males volunteers underwent a sham-feeding experiments (you chew but do not swallow your food) after an overnight fast with 3-min chewing of water, high-fat (nuts), high-carbohydrate (cereal) or high-protein (cheese) food provided in a randomized order (on four separate occasions). While plasma glucose levels increased slightly and plasma lipids decreased slightly after all test foods, the high-carbohydrate food elicited significantly higher insulin, and the high-protein food resulted in higher ghrelin compared to other test sessions. The authors attribute these changes in part to neuronal signals transmitted through the vagal nerve, which can for e.g. stimulate glucagon release, thereby explaining the observed increase in plasma glucose levels after all foods. This study shows that short-term oral exposure to different foods can result in metabolic and hormonal changes that are partly dependent on diet composition. If nothing else, this study points to the fact that chewing is not simply about mechanically preparing food for swallowing – it is far more a process that puts the organism into a nutritive state with distinct metabolic and hormonal changes. Chew your food! @DrSharma Edmonton, AB Zhu Y, Hsu WH, & Hollis JH (2014). Modified sham feeding of foods with different macronutrient compositions differentially influences cephalic change of insulin, ghrelin, and NMR-based metabolomic profiles. Physiology & behavior, 135, 135-42 PMID: 24952264   .

Time To Go Nuts About Nuts?

Nuts are reportedly chock full of all kinds of nutrients and are probably among the healthiest of snacks. However, they are also among the most calorie-dense foods – a small handful of nuts (~30 g) can easily add up to 150-200 cals. So, do high consumers of nuts run the risk of weight gain? This issue is discussed in depth by Sze Yen Tan and colleagues in a paper published in the American Journal of Clinical Nutrition, in which they review the effects of nuts on appetite, food intake, metabolism, and body weight. While eating nuts may not exactly lead to weight loss, most studies find that consumption of “extra” calories as nuts leads to substantially less weight gain than may be expected based on their caloric content. Their review reflect a number of ways in which nuts may have this effect: Effect on hunger and appetite: “…nut ingestion suppresses hunger and desire to eat and promotes fullness. These sensations may aid dietary compensation that offsets much of the energy contributed by nuts. However, strong compensation can also occur independently of reported appetitive effects. This may reflect imprecision in appetite measurement or a truly independent uncharacterized mechanism.” Mastication (chewing): “Nuts require considerable oral processing effort and this may, in part, account for the often-noted less-than-predicted effect of their consumption on body weight. The mechanical act of chewing reportedly generates satiation signals through cognitive, neural, endocrine, and physical (eg, gastric emptying) mechanisms; augments cephalic phase responses linked to appetite; influences digestion efficiency; modestly increases energy expenditure; and elicits dietary compensation.” Nutrient absorption: “A number of studies have evaluated the efficiency of energy absorption from ground and tree nuts through feeding trials. All showed substantive increases in fecal fat loss with nut consumption, although the values ranged widely from ∼5% to >20%” Energy expenditure: “Collectively, there is some evidence that nut consumption increases thermogenesis, but the data are not robust and there is no clear mechanism. One possibility is that the lipid from nuts is absorbed over a prolonged period of time, leading to a small but sustained source of substrate that fuels thermogenesis and could appear as an increase in REE.” Fat metabolism: “It has been proposed that nut consumption elevates fat oxidation and preferentially reduces body fat mass, especially in the viscera. These actions are attributed to their high unsaturated fat content….Human studies incorporating different nuts into the diet at… Read More »

Obesity Weekend Roundup, November 29

As not everyone may have a chance during the week to read every post, here’s a roundup of last week’s posts: Does Increased Chewing Reduce Food Intake? PTSD Risk Factor For Weight Gain Managing Chronic Post-Surgical Pain Syndromes BMI Does Not Affect Outcomes in Knee-Replacement Surgery Have a great Sunday! (or what is left of it) @DrSharma Edmonton, AB