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New Study: Is A Calorie A Calorie?

A novel study inwards JAMA led past times MD Cara B. Ebbeling in addition to colleagues purports to challenge the thought that all calories are as fattening (1).  Let's have got a look.  When thinking well-nigh the role of calorie intake inwards torso fatness, at that spot are basically iii camps:

1.    Calories don’t affair at all, alone diet composition matters.
2.    Calories are the alone thing that matters, in addition to diet composition is irrelevant.
3.    Calories matter, but diet composition may also play a role.

The commencement i is an strange seat that is non real good populated.  The minute i has a lot of adherents inwards the enquiry world, in addition to there’s plenty testify to brand a practiced illustration for it.  It’s represented past times the phrase ‘a calorie is a calorie’, i.e. all calories are as fattening.  #1 in addition to #2 are both extreme positions, in addition to as such they teach a lot of attention.  But the 3rd group, although less vocal, may live closest to the truth. 
A Little Background on Food Intake, Diet Composition in addition to Energy Expenditure

The loose energy content of the human torso is determined past times the total of loose energy coming in, minus the loose energy exiting—simple on paper.  Since torso fatty is past times far the top dog loose energy storage site inwards the body, it follows that the remainder betwixt loose energy intake in addition to loose energy expenditure determines fatty mass, in addition to this has been experimentally confirmed many times.  But here’s the catch—energy expenditure is non ever constant.  For example, nosotros know that it increases as a mortal gains weight, in addition to decreases when a mortal loses weight (2).  The decrease inwards loose energy expenditure amongst weight loss is caused past times 2 things, 1) a smaller torso requires fewer calories for maintenance, 2) a decrease inwards leptin, which decreases the metabolic charge per unit of measurement past times acting inwards the encephalon (3).

Some people have got suggested that the type of nutrient nosotros eat, non simply the amount, influences loose energy expenditure, in addition to inwards item that this is related to the diet's saccharide content.  In people who are non trying to lose weight (4, 5), or who are beingness overfed (6, 7), the carbohydrate:fat ratio inwards the diet has niggling or no detectable touching on on loose energy expenditure, in addition to if anything it favors carbohydrate, but could this live unlike during fatty loss inwards people who start off overweight?  This thought has been called the ‘metabolic advantage’, most notably attributed to the low-carbohydrate diet.  The thought hither is that you lot tin lose fatty eating the same number of calories if saccharide is kept low.

I’ve never truly weighed inwards on this because it’s a subject of heated debate, in addition to inwards whatever illustration it’s a fairly academic question.  Why is it academic?  Because previous weight loss studies have got shown that if a metabolic wages exists at all, it’s quite small, because the consequence is undetectable inwards most studies (8, 9, 10).  People who are non associated amongst the low-carbohydrate community tend to conclude that there's no metabolic wages when they review the literature (11), although I haven't reviewed it closely myself.  It’s clear that where fatty loss is concerned, calorie intake is much to a greater extent than of import than the total of fatty or saccharide inwards the diet.  What previous studies have got suggested is that low-carbohydrate diets suppress appetite — oft resulting inwards lower calorie intake (12, 13).  The argue for this remains a subject of speculation.  

That beingness said, I’m truly quite opened upwards to the thought that nutrient character inwards add-on to quantity tin influence torso fatness, in addition to I would encourage people to remember exterior the macronutrient box: at that spot are belike many unlike dietary factors that tin have got such an effect.  Although this thought hasn’t received much back upwards inwards the human literature thence far, there’s quite a combat of testify for it inwards the beast literature.  For example, when nosotros desire to create obesity inwards rodents nosotros typically utilisation diets that are composed of refined ingredients, high inwards fatty (40-60% of calories), comprise about refined saccharify ( 10% of calories), in addition to are highly palatable.  These diets are extremely fattening inwards susceptible strains, but their fattening powerfulness is alone partially subject on increased calorie intake.  If you lot bound an animal's loose energy intake thence that it’s the same as rodents on a non-fattening unrefined diet (called ‘pair feeding’), they even thence gain most of the fatty that they would have got if you lot hadn’t restricted loose energy intake at all (14, 15)!  This suggests that these diets brand their bodies ‘want’ to live fat, in addition to they volition accomplish this finish past times increasing calorie intake and/or past times decreasing loose energy expenditure.  This is related inwards large component division to changes that occur inwards the brains of these animals (16)

The Study

Enter the recent study past times MD David Ludwig’s grouping (1).  This is a truly fascinating, about mightiness tell groundbreaking, study.  Although nosotros know that differences inwards dietary saccharide in addition to fatty content have got niggling or no touching on on loose energy expenditure during overfeeding, inwards weight-stable people, or during weight loss, nosotros don’t know much well-nigh how these touching on loose energy expenditure during weight maintenance later weight loss.  Weight maintenance is critical because it’s where most people’s weight loss efforts fail. 

Contrary to about of the claims I'm sure are beingness made well-nigh this study, it wasn’t truly designed to enjoin whether fatty in addition to saccharide per se influence loose energy expenditure.  What they compared were iii distinct dietary patterns that differed inwards carbohydrate, fat, protein, in addition to other aspects of diet composition, although saccharide content was sure enough a major departure betwixt groups. 

In this study, they started amongst overweight in addition to obese volunteers who had lost an average of xiv per centum of torso weight using a low-calorie diet.  Then they placed them on iii unlike diets, which were exactly controlled past times the investigators:
  1. A low-fat (LF) diet  “designed to reverberate conventional recommendations to cut back dietary fat, emphasize whole grain products, in addition to include a multifariousness of vegetables in addition to fruits”.  60-20-20 carbohydrate-fat-protein.  I remember these people were eating a lot of breads, pastas, etc. 
  2. A depression glycemic index (LGI) diet diet designed to “achieve a moderate glycemic charge past times replacing about grain products in addition to starchy vegetables amongst sources of healthful fatty in addition to low–glycemic index vegetables, legumes, in addition to fruits”.  40-40-20 carbohydrate-fat-protein.  Low glycemic index carbohydrates are those that increment blood refined saccharify less per unit of measurement saccharide eaten, such as beans, oatmeal, fruit, in addition to sweetness potatoes.
  3. A real depression saccharide (VLC) diet that was “modeled on the Atkins Diet in addition to had a depression glycemic charge due to to a greater extent than severe restriction of carbohydrate”.  10-60-30 carbohydrate-fat-protein.  This is generally meat, vegetables, eggs, nuts, in addition to added fats.  They also took a fiber supplement as recommended past times Atkins.
After 4 weeks, they measured loose energy expenditure, both at ease in addition to over the assort of 24 hours.  It’s worth mentioning that they used the world of the fine art techniques to mensurate these variables.  What they flora is that loose energy expenditure at rest, in addition to over 24 hours, was highest inwards the VLC group, intermediate inwards the LGI, in addition to lowest inwards the LF group—and the differences were substantial, upwards to 308 calories a day.  H5N1 notable limitation of this study is that each diet menstruum alone lasted 4 weeks—we don’t know what would have got happened to these people later half-dozen months or a year.

Does this back upwards the thought that at that spot is a ‘metabolic advantage’ to low-carbohydrate diets?  Well, sort of.  It doesn’t alter the previous findings that the carbohydrate:fat ratio has niggling or no touching on on loose energy expenditure during overfeeding, inwards weight stable people, or during weight loss, but it does propose that a VLC dietary pattern has a metabolic wages over a LF diet specifically inwards the context of weight maintenance later weight loss.  It also suggests that a LGI diet has a smaller but even thence meaningful metabolic wages inwards this setting, in addition to that a LF diet are non real effective inwards this regard.  It also opens a whole novel tin of worms for the enquiry world, investigating the effects of diet character on loose energy expenditure. 

So should everyone consume a VLC diet for weight loss maintenance then?  Not thence fast.  The VLC diet grouping experienced about troubling hormonal changes that seem to live pretty mutual amongst this variety of diet.  There were iii top dog negative changes.  The commencement in addition to maybe most troubling was an increment inwards cortisol, a stress hormone that may contribute to serious wellness problems over the long term (17).  The minute was a decrease inwards thyroid hormone, which is something that has been observed repeatedly amongst this variety of diet.  Many of the negative effects that about people develop on long-term VLC diets (constipation, lethargy, pathetic sleep, pilus loss, irritability) could live related to depression thyroid function.  This doesn't seem to live as much of an number amongst moderate saccharide restriction.  The 3rd was an increment inwards C-reactive poly peptide (CRP), a mark of inflammation in addition to midpoint prepare on risk.  Although the newspaper in addition to media reports brand a large bargain out of the increment inwards CRP, it looks quite modest to me—I’m non convinced it’s biologically significant. 

The low-fat diet came out looking pretty pathetic as well.  Energy expenditure was lowest on this diet, in addition to estimated insulin sensitivity was also lowest (although the caveat hither is that they didn't straight mensurate insulin sensitivity).  This is interesting because as they remarked inwards the paper, this is the dietary advice most people volition have from nutrition authorities.  This adds to the testify that eating a bunch of whole grain breads in addition to pastas is belike non a peachy strategy for weight loss maintenance.

Overall, the LGI diet came out looking the best overall.  It’s the to the lowest degree restrictive of the three, conferred a pretty practiced ‘metabolic advantage’, in addition to was non associated amongst harmful hormonal changes.  I remember this variety of diet would live a reasonable selection for weight maintenance next fatty loss.  I’ve been skeptical of the glycemic index concept inwards the past, in addition to I move on to be, because most controlled studies have got shown that inwards isolation it has niggling or no touching on on torso weight or insulin sensitivity (18, 19).  The LGI diet inwards this study did indeed have got a depression glycemic index, but since it differed from the other diets inwards many other ways, nosotros can’t know whether the glycemic index per se was a relevant factor. 

In whatever case, a diet that focuses on beans/lentils, meats, nuts, fruits, in addition to vegetables at the expense of grains (particularly flours) may live a practiced selection for weight loss maintenance, in addition to I remember this squares good amongst enquiry coming from other angles.  That beingness said, at that spot are about major caveats to this study that must live kept inwards mind:
  1. It was alone 4 weeks long.  We don't know if this departure would have got continued inwards the long run.
  2. The study was non designed to mensurate long-term changes inwards fatty mass, which is what we're ultimately interested in.
  3. This was done nether calorie-controlled conditions, non nether free-living atmospheric condition as most people would apply these diets.  Under free-living conditions, the top dog determinant of long-term fatty loss seems to live how good you lot stick to a diet, non which diet you lot lead (20, 21, 22).
  4. There was a lot of private variability inwards this study, confirming i time once to a greater extent than that everyone is different.  There is no argue to stick to a diet if it's non working for you, simply because a study says it plant good for the "average person".  Kudos to Drs. Ebbeling in addition to Ludwig for reporting private data.
Despite these of import caveats, I remember the results are fascinating in addition to I hold back forrad to to a greater extent than studies on this phenomenon.  If I have got time, I may hash out the potential mechanisms for this consequence inwards a time to come post.

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