New study purports to show 250 calorie benefit to low-carb

I'm no expert but I read through it and it looks to have been a very well thought out and put together study. Interesting find. When I have more time is like to dig into the methods of calculations they used and learn about them.

All data is just data.. I'd like to see similar tests with similar results, but that is very interesting.

Not sure if serious

Highlights:

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Energy intake was restricted to 60% of estimated needs.

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During the test phase, high, moderate, and low carbohydrate diets varied in carbohydrate (60%, 40%, and 20% of total energy, respectively) and fat (20%, 40%, and 60%, respectively), with protein fixed at 20%

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We controlled for protein, in view of its higher thermic effect,29 to provide a more specific test of the carbohydrate-insulin model. The relative amounts of added sugar (15% of total carbohydrate), saturated fat (35% of total fat), and sodium (3000 mg/2000 kcal) were held constant across diets.

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Total energy expenditure (primary outcome) was assessed using the doubly labeled water method.

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We expressed total energy expenditure in kcal per kg body weight, then normalized this to average start of trial body weight (82 kg) for analysis and reporting. This approach takes into account small changes in body weight that might occur during the test phase, within our definition of weight loss maintenance (within 2 kg of the start of the trial weight), and thereby improve precision. Some investigators discourage adjustment of total energy expenditure for weight because of confounding that would arise from individual differences in relations between total energy expenditure and body weight, body composition, and metabolically active mass.38 However, this problem, inherent to cross sectional comparisons between people, would not apply to the within individual comparisons over several months in our study, especially during weight loss maintenance when these relations would not change in any meaningful way. We also examined absolute total energy expenditure expressed as kcal/d, with and without body weight included as a covariate, and we obtained similar results.

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The target of 135 completers provided 80% power, with 5% type I error, to detect a difference of 237 kcal/d in total energy expenditure change between one diet group and the other two diet groups. This difference is smaller than the effect detected in the previous study39 and is consistent with a predicted effect of 50 kcal/d per 10% decrease in the contribution of carbohydrate to total energy intake.

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high (n=54), moderate (n=53), or low (n=57) levels of carbohydrate.

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Ghrelin (intention-to-treat and per protocol analyses) and leptin (per protocol analysis only) differed significantly by diet. Ghrelin showed a steeper decline over the test phase in participants assigned to the low carbohydrate compared with high carbohydrate diet, and leptin showed a lesser incline.

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Also, as expected, triglyceride levels increased with increasing carbohydrate content (P<0.001), whereas levels of high density lipoprotein cholesterol decreased (P<0.001).

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controlled feeding trial over 20 weeks,

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A change in metabolism is suggested by hormonal responses to diet. Ghrelin, produced primarily in the stomach, was significantly lower in participants assigned to the low carbohydrate diet, a novel finding. Beyond effects on hunger, ghrelin has been reported to lower energy expenditure and promote fat deposition,6465 providing another mechanistic explanation for our primary outcome. Leptin (an adipocyte hormone that signals body energy stores) was also lower in participants assigned to the low carbohydrate diet, suggesting improvement in leptin sensitivity.66 Prospective studies have observed that people with the greatest declines in leptin levels after weight loss have the lowest risk for weight regain.676869

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is a large controlled feeding study among free living participants

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The study has three main limitations, including potential measurement error, non-compliance, and generalizability.

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We considered our protocol too long to be logistically practical or financially feasible for an inpatient setting. Instead, we provided participants with fully prepared meals, and implemented strategies to promote compliance with the assigned diets.20 Despite these efforts, we recognize that non-compliance could have occurred, especially among those whose weight deviated beyond the prespecified definition of weight loss maintenance

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The third limitation of our study is translation of findings from feeding studies to public health recommendations.

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A quick gathering of notes after a look-over. I'll be spending the next few days away from my laptop, but when I get back I will dive deeper into the details. A decent 4 month study. Now we need 3 more just like it to get the subject numbers up .

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During the test phase, high, moderate, and low carbohydrate diets varied in carbohydrate (60%, 40%, and 20% of total energy, respectively) and fat (20%, 40%, and 60%, respectively), with protein fixed at 20%

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Even at the lowest 20% is much too high for a true look at this issue. The traditional Keto diet is 5% or <20g of net carbs whichever is less.

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Ghrelin (intention-to-treat and per protocol analyses) and leptin (per protocol analysis only) differed significantly by diet. Ghrelin showed a steeper decline over the test phase in participants assigned to the low carbohydrate compared with high carbohydrate diet, and leptin showed a lesser incline

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The Ghrelin reduction is interesting. I wonder how fiber/fluid intake was monitored? Raw math would suggest a ghrelin increase from switching a 4kCal/g macro with a 9kCal/g macro (less stomach stretching from eating). But, I guess compared to a starch, "Fatty foods" such as meats contain their fair bit of non-digestable material.

Leptin increase is pretty straight forward if pre-digested dietary fats can cause a leptin response instead of waiting for your body's stored fat to do it. In essence this would be you 'tricking' your body into thinking you're getting fat (or fatter) so your horomones act to try to get you to eat less.

I think this study may show that nmacro adjustments can be a key in helping with casual obesity (slow upward drift in weight in adulthood, "dad bod", etc..) where a slight change in horomonal balance can offset being 100kCal/day hungrier than you need to be on a daily basis.

But, this probably doesn't begin to touch extreme obesity where the body is ignoring horomonal signals to begin with.

Ghrelin goes down while you fast.