Dietary Restraint and Cortisol Levels – Research Review

I don’t think I’ve done a research review in a while and even though I imagine some visitors to the site may be getting tired of topics related to the book I’m working on, well, that’s what I’m currently working on so it’s kind of at the top of my mind right now.

Today, I want to do a research review but for various reasons, mainly the abstract being too long to paste, I want to do it a little bit differently. The paper I want to look at is titled

McLean JA et. al. Cognitive dietary restraint is associated with higher urinary cortisol excretion in healthy premenopausal women. Am J Clin Nutr. 2001 Jan;73(1):7-12. And you can get the free full text here.

Background

I imagine most visitors to my site are familiar with the hormone cortisol, even if many aren’t quite clear on what it does. Cortisol is often thought of as a “bad” hormone but this is too simplistic; what cortisol does in the body depends on a host of factors. The primary of these is whether it is released in a pulsatile and acute fashion (basically small pulses) or is elevated chronically. The first situation tends to be adaptive, the second tends to cause problems (for more details check out my still favorite book Why Zebras Don’t Get Ulcers by Robert Sapolsky).

So while acute pulses of cortisol help to mobilize fat, stimulate immune system function and improve memory, chronically elevated levels of cortisol may cause fat storage (especially in the face of high insulin), depress immune system function and harm memory. Basically, acute increases (that go down afterwards) are good, chronic increases (from chronic stress) are bad.

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Impact of the Menstrual Cycle on Determinants of Energy Intake – Research Review

L Davidsen et. al. Impact of the menstrual cycle on determinants of energy balance: a putative role in weight loss attempts. International Journal of Obesity (2007) 31, 887-890

Abstract: Women’s weight and body composition is significantly influenced by the female sex-steroid hormones. Levels of these hormones fluctuate in a defined manner throughout the menstrual cycle and interact to modulate energy homeostasis. This paper reviews the scientific literature on the relationship between hormonal changes across the menstrual cycle and components of energy balance, with the aim of clarifying whether this influences weight loss in women. In the luteal phase of the menstrual cycle it appears that women’s energy intake and energy expenditure are increased and they experience more frequent cravings for foods, particularly those high in carbohydrate and fat, than during the follicular phase. This suggests that the potential of the underlying physiology related to each phase of the menstrual cycle may be worth considering as an element in strategies to optimize weight loss. Studies are needed to assess the weight loss outcome of tailoring dietary recommendations and the degree of energy restriction to each menstrual phase throughout a weight management program, taking these preliminary findings into account.

 

Background

Amusingly, given the project I am currently finishing up (I promise, it’s coming along), I had run this piece back in 2009.  But since I am currently at a loss as to what to write about today, it seemed appropriate to run it again.  And yes, all of this will be covered in detail in the upcoming book along with ways to address and/or fix it.

Compared to men, women get the short end of the stick in almost everything related to body composition. Their bodies fight back harder, they lose both weight and fat slower (even given an identical intervention), they gain muscle more slowly, etc.  Then again, they do get that whole multiple orgasm thing so there is at least some good that comes along with the bad.

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Reduced Fat and Reduced Carbohydrate Diets and Fat Loss – Research Review

Hall, KD et. al. Calorie for Calorie, Dietary Fat Restriction Results in More Body Fat Loss than Carbohydrate Restriction in People with Obesity Cell Metabolism  Cell Metabolism (2015) 22: 1–10.

Abstract

Dietary carbohydrate restriction has been purported to cause endocrine adaptations that promote body fat loss more than dietary fat restriction. We selectively restricted dietary carbohydrate versus fat for 6 days following a 5-day baseline diet in 19 adults with obesity confined to a metabolic ward where they exercised daily. Subjects received both isocaloric diets in random order during each of two inpatient stays. Body fat loss was calculated as the difference between daily fat intake and net fat oxidation measured while residing in a metabolic chamber. Whereas carbohydrate restriction led to sustained increases in fat oxidation and loss of 53 ± 6 g/day of body fat, fat oxidation was un- changed by fat restriction, leading to 89 ± 6 g/day of fat loss, and was significantly greater than carbohydrate restriction (p = 0.002). Mathematical model simulations agreed with these data, but predicted that the body acts to minimize body fat differences with prolonged isocaloric diets varying in carbohydrate and fat.

Background on Reduced Fat and Reduced Carbohydrate Diets

For years the debate over reduced fat or reduced carbohydrates has gone on and it shows no sign of stopping.  The pendulum has actually swung over the years.  In the 70’s, the Atkins diet drove interest in very low/reduced carbohydrate diets.  In the 80’s, reduced fat diets came into vogue as it looked like dietary fat was more easily stored as body fat and it looked like, so long as fat intake was kept low enough, weight and fat loss would happen (this was true until people went nuts and started overeating low fat foods in excess).  In the 90’s, somehow the Zone caught on and then things started to fragment.  Cyclical ketogenic/reduced carbohydrate diets became popular and I even wrote an entire book on the topic.

But now, with the joys of the Internet, the entire dietary world has become very divided.  With the publication of a book that I shall not name the idea that insulin was the cause of obesity, that reducing insulin was either required or would magically cause fat loss came back into vogue.  Nevermind that the entire insulin hypothesis has been completely destroyed.

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The Dieters Paradox – Research Review

Chernev A.  The Dieters Paradox.  Journal of Consumer Psychology.  (2001) 21: 178-183.

Abstract
Despite the vast public policy efforts to promote the consumption of healthy foods and the public’s growing concern with weight management, the proportion of overweight individuals continues to increase. An important factor contributing to this obesity trend is the misguided belief about the relationship between a meal’s healthiness and its impact on weight gain, whereby people erroneously believe that eating healthy foods in addition to unhealthy ones can decrease a meal’s calorie count. This research documents this misperception, showing that it is stronger among individuals most concerned with managing their weight—a striking result given that these individuals are more motivated to monitor their calorie intake. This finding has important public policy implications, suggesting that in addition to encouraging the adoption of a healthier lifestyle among overweight individuals, promoting the consumption of healthy foods might end up facilitating calorie overconsumption, leading to weight gain rather than weight loss.

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Background

In introducing today’s paper, I am reminded of an old joke/quip to the effect that “All that separates man from the animals is our ability to rationalize.”   I’d add “And accessorize” but that’s neither here nor there.  But the reality is that humans are able to do a wide variety of mental gymnastics in how they approach life.  Effectively, we appear to be slave to what psychologists call cognitive biases, ways in which we think about the present, past, future or ourselves that often lead us to make some fascinatingly bad choices.  This is a topic that many recent books has discussed in a variety of contexts.

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Mind Over Milkshakes: Mindsets, Not Just Nutrients, Determine Ghrelin Response – Research Review

Mind over milkshakes: Mindsets, not just nutrients, determine ghrelin response.  Crum AJ et. al.  Health Psychol. 2011 May 16. [Epub ahead of print]

Objective: To test whether physiological satiation as measured by the gut peptide ghrelin may vary depending on the mindset in which one approaches consumption of food. Methods: On 2 separate occasions, participants (n = 46) consumed a 380-calorie milkshake under the pretense that it was either a 620-calorie “indulgent” shake or a 140-calorie “sensible” shake. Ghrelin was measured via intravenous blood samples at 3 time points: baseline (20 min), anticipatory (60 min), and postconsumption (90 min). During the first interval (between 20 and 60 min) participants were asked to view and rate the (misleading) label of the shake. During the second interval (between 60 and 90 min) participants were asked to drink and rate the milkshake. Results: The mindset of indulgence produced a dramatically steeper decline in ghrelin after consuming the shake, whereas the mindset of sensibility produced a relatively flat ghrelin response. Participants’ satiety was consistent with what they believed they were consuming rather than the actual nutritional value of what they consumed. Conclusions: The effect of food consumption on ghrelin may be psychologically mediated, and mindset meaningfully affects physiological responses to food. (PsycINFO Database Record (c) 2011 APA, all rights reserved).

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Background

Ok, in addition to having possibly the coolest title of any paper I’ve reviewed on the site, this is also one of the weirdest papers I’ve looked at.  But I’ve seen it getting a lot of press and, of course, have to put in my own two cents, if for no other reason than I suspect many people will take the findings far out of context.  First, some necessary background; this will probably take more space than discussing the actual paper itself.

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