Wednesday, July 30, 2014

Prebiotic Fibre Alters Mother Milk and Offspring Gut Bacteria in Rats

sharma-obesity-suckling-rat1With all the attention to the role of gut microbiota and the ongoing debate as to the role of breast feeding in obesity prevention, a study by Raylene Reimer and colleagues from the University of Calgary adds an interesting spin.

Their study, now published in OBESITY shows that feeding female rat a diet high in prebiotic fibre (21.6% wt/wt) throughout pregnancy and lactation, compared to a control or high-protien (40% wt/wt) diet, results in a lower oligosaccharide content of the milk with a higher content of bifidobacteria in the offspring.

Although this did not lead to any marked differences in body composition or other metabolic parameters, the study proves the point that (at least in rats) maternal diet can affect the composition of gut bacteria in the offspring (which may or may not have metabolic benefits).

There is no reason to believe that in humans maternal nutrition may well impart a similar influence via breast feeding on the microbiota of infants.

This certainly sounds like a promising field for future research.

@DrSharma
Edmonton, AB

ResearchBlogging.orgHallam MC, Barile D, Meyrand M, German JB, & Reimer RA (2014). Maternal high protein or prebiotic fiber diets affect maternal milk composition and gut microbiota in rat dams and their offspring. Obesity (Silver Spring, Md.) PMID: 25056822

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Tuesday, July 15, 2014

The Molecular Biology of Food And Mood

sharma-obesity-brainThe neuroendocrine systems that control ingestive behaviour are intimately linked to the parts of the brain that control mood.

Thus, it is increasingly evident that factors that affect energy homeostasis (diet and exercise) can have profound effects on mood while changes in mood can have significant effects on appetite and energy homeostasis.

But this relationship is far from straightforward – rather, it appears to be rather complex.

Readers interested in an overview of how these two systems interact in the brain may find a recent review by Chen Liu from the University of Texas Southwestern Medical Center, Dallas, published in Cell Metabolism of interest.

The authors review our current understanding of how mood and food are linked with particular attention to appetite, ingestive behaviour and energy homeostasis.

The article also touches on the effects of pharmacological and surgical treatments for obesity on mood.

Clearly clinicians need to be aware of the close links between these systems and draw on our current understanding of both in their counselling of patients presenting with weight gain and/or depression.

@DrSharma
Edmonton, AB

ResearchBlogging.orgLiu C, Lee S, & Elmquist JK (2014). Circuits Controlling Energy Balance and Mood: Inherently Intertwined or Just Complicated Intersections? Cell metabolism, 19 (6), 902-909 PMID: 24630814

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Thursday, July 10, 2014

Can Germs In Your Drinking Water Help Prevent Obesity?

sharma-obesity-tap-water1In my show I joke about how I intend to import water from the river Ganges as a new obesity treatment that I will appropriately name “RunFast”.

Jokes aside, a study by Zhongyi Chen and colleagues, published in the Journal of Clinical Investigation, shows that treating mice with genetically modified bugs delivered through their drinking water can protect them from becoming obese even when fed a high-fat diet.

To be exact, the researchers used a strain of e coli bacteria genetically engineered to produce N-acylphosphatidylethanolamines (NAPEs), which are precursors to the N-acylethanolamide (NAE) family of lipids, normally synthesized in the small intestine in response to feeding and known to reduce food intake.

As their study shows, administration of these modified bacteria in drinking water for 8 weeks dramatically lowered food intake, weight gain, body fat, insulin resistance and liver fat in mice on a high-fat diet.

These “protective effects” lasted for at least 4 weeks after removal of these bacteria from the drinking water.

In another set of experiments the researchers also showed that this strain of bacteria reduced weight gain in a genetic model of mouse obesity.

Contrary to what one may believe, this study neither supports nor refutes the idea that gut bacteria may be partly responsible for the obesity epidemic.

Rather, the study primarily shows that bacteria may be used as a delivery system for “therapeutic doses” of molecules to the intestines – in this case, resulting in the modification of appetite and metabolism.

I would not be surprised if the therapeutic use of bacteria (genetically modified or not) opens up a whole new dimension of therapeutics – not just for obesity.

@DrSharma
Edmonton, AB

ResearchBlogging.orgChen Z, Guo L, Zhang Y, L Walzem R, Pendergast JS, Printz RL, Morris LC, Matafonova E, Stien X, Kang L, Coulon D, McGuinness OP, Niswender KD, & Davies SS (2014). Incorporation of therapeutically modified bacteria into gut microbiota inhibits obesity. The Journal of clinical investigation PMID: 24960158

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Tuesday, June 24, 2014

Time To Go Nuts About Nuts?

sharma-obesity-nutsNuts 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 realistic doses are needed to determine the effect of nut consumption on body composition.”

With regard to impact on body weight, the authors reach the following conclusions:

Adding nuts to habitual diets:

“Although there are reports of small, but significant increases in body weight with nut consumption, the preponderance of evidence indicates that under controlled or free-living situations, nut consumption does not promote weight gain.”

Eating nuts in calorie-restricted diets:

“The inclusion of nuts in energy-restriction regimens does not impede weight loss. In several trials in which nuts did not augment weight loss, there was a reduction in cardiovascular disease risk indexes in the nut-consuming groups, suggesting that such benefits derive from properties of the nuts rather than just weight change.”

Eating nuts in weight maintenance:

“Several studies assessing the role of nut consumption in weight-maintenance programs have noted a decrease in body weight from baseline. Whether this is due to a greater thermic effect of food or REE effect of the nuts compared with the foods they displaced in the diet has not been established. Nevertheless, current data indicate that the inclusion of nuts in a weight-maintenance program will not lead to weight gain and may aid weight loss.”

Thus, in summary, the authors conclude that,

“…evidence indicates that they pose little challenge to and may even aid weight management. This is attributable to the strong dietary compensation effects they elicit, inefficiency in the absorption of the energy they provide, and possibly an elevation of energy expenditure and fat oxidation.”

As a general caveat to all of these data, it needs to be noted that results varied widely depending on the types of nuts and how exactly these nuts were consumed (e.g. as snacks or added to meals – the former often being more favourable than the latter).

Also, many of the studies had relatively small number of participants and were of rather short duration.

Nevertheless, it does appear that going nuts about nuts may not be quite as detrimental to your weight as their energy content would suggest.

@DrSharma
Toronto, ON

ResearchBlogging.orgTan SY, Dhillon J, & Mattes RD (2014). A review of the effects of nuts on appetite, food intake, metabolism, and body weight. The American journal of clinical nutrition, 100 (Supplement 1) PMID: 24920033

 

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Monday, June 23, 2014

Does More Energy In And Out Make It Easier To Maintain Energy Balance?

sharma-obesity-caloric_balance_scaleFrom every thing we know about obesity, the simplistic model of energy-in-energy-out (or Eat-Less-Move-More) approach to managing weight has not led us to any meaningful advances in obesity management. The number of people who can successfully manage their weight by this approach in the long-term is so minuscule, that every “success story” is considered “newsworthy”.

Now, a provocative paper by Gregory Hand and Steven Blair, published in US Endocrinology, suggests that what matters for good health is the amount of energy flowing through the system rather than the state of energy balance.

Thus,

“Recent findings suggest that a high energy flux, maintained by increasing energy expenditure, can improve an individual’s metabolic profile without changing weight.”

This, essentially, is a fancy way of saying, that simply moving more calories through your body by burning more calories (even if you instantly eat them back) benefits the organism irrespective of any impact this may have on body weight – or that exercise is good for you even if you do not lose weight.
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Anyone familiar with Steven Blair’s work (fat and fit is better than skinny and unfit) – will recognize the theme – but couching it in a concept of energy flux is a novel and interesting spin to this idea.

Apart from providing a theoretical model for how exercise may benefit you even if you don’t lose any weight doing it, the model may also have implications for weight management.

Thus,

“The significance of the model of energy regulation is twofold: First, the model suggests that energy balance, and maintaining a stable weight is more easily achieved at a high energy flux. Second, a high energy flux can be achieved by matching a high energy intake with equivalent high energy expenditure, or by increasing energy stores (gaining weight). Of note is that these two characteristics of the model suggest that the biological system was designed to maintain a high energy flux, and increasing energy stores is a quite viable mechanism to achieve this level of energetics. An extensive body of research indicates that multiple and redundant mechanisms regulate the ‘drive’ for energy intake. The high energy flux is attained by matching the intake with expenditure and/or a change in energy storage. Weight gain is consistent with high energy flux combined with low energy expenditure, and it follows that attempting to achieve energy balance at a low energy flux (sedentary behavior combined with food restriction) is not a long-term strategy for weight maintenance.”

The biological question that pops into my mind of course is as to how exactly the body would sense this “flux”. While it is easy to see how the body would sense energy stores (e.g. through hormonal signals such as leptin), it is not clear how the body would monitor flux (after all, to regulate something, it needs to be measured).

This is not something that the authors delve into, thus leaving a somewhat unsatisfying gap in what otherwise makes for an interesting hypothesis.

@DrSharma
Toronto, ON

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In The News

Diabetics in most need of bariatric surgery, university study finds

Oct. 18, 2013 – Ottawa Citizen: "Encouraging more men to consider bariatric surgery is also important, since it's the best treatment and can stop diabetic patients from needing insulin, said Dr. Arya Sharma, chair in obesity research and management at the University of Alberta." Read article

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