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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Effects of Low Versus High Load Resistance Training – Research Review

Schoenfeld BJ et. al. Effects of Low Versus High Load Resistance Training on Muscle Strength and Hypertrophy in Well-Trained Men.J Strength Cond Res. 2015 Apr 3. [Epub ahead of print]

Abstract

The purpose of this study was to compare the effect of low- versus high-load resistance training (RT) on muscular adaptations in well-trained subjects. Eighteen young men experienced in RT were matched according to baseline strength, and then randomly assigned to 1 of 2 experimental groups: a low-load RT routine (LL) where 25-35 repetitions were performed per set per exercise (n = 9), or a high-load RT routine (HL) where 8-12 repetitions were performed per set per exercise (n = 9). During each session, subjects in both groups performed 3 sets of 7 different exercises representing all major muscles. Training was carried out 3 times per week on non-consecutive days, for 8 total weeks. Both HL and LL conditions produced significant increases in thickness of the elbow flexors (5.3 vs. 8.6%, respectively), elbow extensors (6.0 vs. 5.2%, respectively), and quadriceps femoris (9.3 vs. 9.5%, respectively), with no significant differences noted between groups. Improvements in back squat strength were significantly greater for HL compared to LL (19.6 vs. 8.8%, respectively) and there was a trend for greater increases in 1RM bench press (6.5 vs. 2.0%, respectively). Upper body muscle endurance (assessed by the bench press at 50% 1RM to failure) improved to a greater extent in LL compared to HL (16.6% vs. -1.2%, respectively). These findings indicate that both HL and LL training to failure can elicit significant increases in muscle hypertrophy among well-trained young men; however, HL training is superior for maximizing strength adaptations.

Background

For years, it’s been taken basically as an article of faith that the best way to stimulate muscle growth is with relatively heavy loads for lower repetitions.  The hypertrophy zone is usually defined as 8-12 (5-15 is better) repetitions per set with heavy weights.  Muscle fibers are recruited in an order according to the size principle with only the high threshold Type II muscle fibers (the ones most responsible for growth requiring heavy loads of 80-85% for maximal recruitment.

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Effects of different volume-equated resistance training loading strategies on muscular adaptations in well-trained men – Research Review

Schoenfeld BJ et. al. “Effects of different volume-equated resistance training loading strategies on muscular adaptations in well-trained men.” J Strength Cond Res. 2014 Apr 7. 

Regimented resistance training has been shown to promote marked increases in skeletal muscle mass. Although muscle hypertrophy can be attained through a wide range of resistance training programs, the principle of specificity, which states that adaptations are specific to the nature of the applied stimulus, dictates that some programs will promote greater hypertrophy than others. Research is lacking, however, as to the best combination of variables required to maximize hypertophic gains. The purpose of this study was to investigate muscular adaptations to a volume-equated bodybuilding-type training program versus a powerlifting-type routine in well-trained subjects. 17 young men were randomly assigned to either an HT group that performed 3 sets of 10RM with 90 seconds rest or an ST group that performed 7 sets of 3RM with 3 minutes rest. After 8 weeks, no significant differences were noted in muscle thickness of the biceps brachii. Significant strength differences were found in favor of ST for the 1RM bench press and a trend was found for greater increases in the 1RM squat. In conclusion, this study showed both bodybuilding- and powerlifting-type training promote similar increases in muscular size, but powerlifting-type training is superior for enhancing maximal strength.

Introduction

Ok, so assuming you made it through the Categories of Weight Training series re-run/re-write, you hopefully saw that there is a general belief/schema whereby different loading parameters (intensity, volume, etc.) generate differential results in terms of muscular endurance, muscle growth, muscle strength.

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