For those that don’t know anything about the author or the book, John Kiefer holds a bachelor’s degree in Physics and Mathematics as well as a master’s degree in Physics, and is the owner of the Dangerously Hardcorewebsite. In addition to Carb Back-Loading(CBL), Kiefer has written a previous book titled The Carb Nite Solution. From his credentials and by listening to him on various podcasts and YouTube videos, Kiefer comes across as an intelligent and genuinely nice guy, so that’s where the personal judgments stop. As such, in this review, I’ll take a reasonably in depth look at CBL and examine whether the claims behind it withstand scientific scrutiny.Read More
Whole-body protein turnover is the continuous process within the human body by which protein is created (anabolism) and broken down (catabolism), it is believed to occur at a rate of 300 g/day in an average 70 kg man. Whole-body protein turnover is largely regulated by feeding, a number of specific nutritional factors, along with fasting, hormonal factors and certain disease states. Gains in skeletal muscle occur following prolonged periods of net protein deposition; where muscle protein synthesis exceeds net muscle protein breakdown, thus resulting in a net gain in muscle protein (Wagenmakers, 1999).
Humans, especially athletes often seek net gains in muscle protein; such gains enable increased muscle mass and enhance muscle recovery. As mentioned, a number of nutritional and hormonal factors regulate protein synthesis and thus have a significant impact on body composition; the way you look.
Protein intake is known to have a significant effect on whole-body protein turnover, but what effect does fish oil have, if any?
Recent studies have suggested long-chain omega-3 fatty acids enhance the efficiency and effectiveness of insulin pathway signalling, therefore generating mTOR activity. The mammalian target of rapamycin (mTOR) regulates a number of physiological components, including; interestingly protein synthesis. Signalling through the mTOR is activated by amino acids, insulin, and growth factors, but impaired by nutrient or overall energy deficiency.
So mTOR regulates muscle protein synthesis; and mTOR signalling is activated by insulin, the efficiency of which is enhanced by omega-3 fatty acids.
In a study of fish oil supplementation (4 g/day) providing 1.86 and 1.50 g/day EPA and DHA for 8-weeks in nine healthy middle aged subjects, Smith et al (2011a) revealed the anabolic response to insulin and amino acid infusion was greater in those subjects supplemented fish oils. In addition, muscle protein concentration and muscle cell size were both greater after fish oil supplementation; clearly demonstrating fish oil aids the activation of mTOR. This has previously been demonstrated in older adults (Smith et al. 2011b), and Gingras et al (2007) also demonstrated a positive effect of fish oil supplementation on mTOR activation and subsequent muscle protein synthesis through enhanced insulin signalling.
This apparent activation of the insulin signalling pathway is thought to derive from the anti-inflammatory effects of long-chain omega-3 fatty acids. Insulin resistance is associated with chronic inflammation; both EPA and DHA exert significant anti-inflammatory effects, and actively reduce inflammatory signalling molecule production. In an intricate study on mice, Young Oh et al. (2010) reported omega-3 fatty acid supplementation inhibited inflammation and enhanced insulin sensitivity. A similar mechanism has also been demonstrated in humans, Tsitouras et al. (2008) revealed adults fed a high omega-3 fatty acid diet for 8-weeks increased insulin sensitivity through improved inflammatory status.
So how is that of benefit?
Well supplementation of omega-3 fatty acids increase insulin sensitivity which allows for more effective activation of the insulin signalling pathway ultimately leading to mTOR stimulation and muscle protein synthesis. Increasing insulin sensitivity also has a significant effect on a number of other physiological functions including an increase in glucose and fatty acid uptake by muscle cells (Goodpaster et al. 2003); directing nutrients to muscle cells for oxidation (energy production) rather than fat storage, improving overall body composition and providing more fuel for muscle during exercise.
So omega-3 supplementation can activate the body’s muscle making systems and improve body composition?
Well, yes. A randomized double-blind study on 44 middle aged men and women supplemented either 4 g/day omega-3 fatty acids providing 1,600 mg/day EPA and 800 mg/day DHA, or 4 g/day safflower oil for 6-weeks revealed omega-3 fatty acid supplementation significantly increased fat free mass (body mass minus fat mass), significantly reduced fat mass, and had a tendency to reduce body fat percentage (Noreen et al. 2010).
These studies highlight a mechanism that eludes omega-3 fatty acid supplementation can significantly improve body composition. Stemming from the anti-inflammatory capacity of both EPA and DHA, omega-3 fatty acids can increase insulin sensitivity which has a knock on effect on muscle anabolism in the presence of dietary carbohydrate and protein (typical of a post-workout meal/supplement) and repartitioning of energy to muscle instead of fat which ultimately results in fat loss. These initial findings require further exploration in more rigorous studies with more participants and in a more controlled setting; although the science is clearly there to be disproved.
Gingras, A., White, P., Chouinard, P., Julien, P., Davis, T., Dombrowski, L.,... & Thivierge, M. (2007). Long-chain omega-3 fatty acids regulate bovine whole-body protein metabolism by promoting muscle insulin signalling to the Akt-mTOR-S6K1 pathway and insulin sensitivity. Journal of Physiology, 579, 269.
Goodpaster, B., Katsiaras, A., & Kelley, D. (2003). Enhanced fat oxidation through physical activity is associated with improvements in insulin sensitivity in obesity. Diabetes, 52, 2191 – 2197.
Noreen, E., Sass, M., Crowe, M., Pabon, V., Brandauer, J., & Averill, L. (2010). Effects of supplemental fish oil on resting metabolic rate, body composition, and salivary cortisol in healthy adults. Journal of the International Society of Sports Nutrition, 7, 31.
Smith, G., Atherton, P., Reeds, D., Mohammed, B., Rankin, D., Rennie, M., & Mittendorfer, B. (2011b). Dietary omega-3 fatty acid supplementation increases the rate of muscle protein synthesis on older adults: a randomized controlled trial. American Journal of Clinical Nutrition, 93, 402.
Smith, G., Atherton, P., Reeds, D., Mohammed, B., Rankin, D., Rennie, M., & Mittendorfer, B. (2011a). Omega-3 polyunsaturated fatty acids augment the muscle protein anabolic response to hyperaminoacidemiahyperinsulinemia in health young and middle aged men and women. Clinical Science (London), 121, 267.
Tsitouras, P., Gucciardo, F., Salbe, A., Heward, C., & Harman, S. (2008). High omega-3 fat intakes improves insulin sensitivity and reduces CRP and IL6, but does not affect other endocrine axes in healthy older adults. Hormonal Metabolism Research, 40, 199.
Wagenmakers, A. (1999). Tracers to investigate protein and amino acid metabolism in human subjects. The Proceedings of the Nutrition Society, 58, 987.
Young Oh, D., Talukdar, S., Bae, E., Imamura, T., Morinaga, H., Fan, W., Olefsky, J. (2010). GPR120 is an omega-3 fatty acid receptor mediating potent anti-inflammatory and insulin sensitizing effects. Cell, 142, 687.
Bio: Matt holds a BSc (Honours) degree in Sport & Exercise Science, an MSc in Nutrition Science. Through his own Performance Nutrition business, Nutrition Condition, he delivers frequent Health & Wellbeing Workshops to corporate and personal clients advising on how best to develop a sound, scientifically structured nutrition programme free from fads and marketing bias. Nutrition Condition also delivers Performance Nutrition services to professional athletes.
For regular updates follow Matt on Twitter @mattNCUK.
Continued from part I
2. Setting protein intake
With the more complicated stuff out of the way, the next step of filling the calories with the macronutrients is really simple.
I discussed the issue of protein requirements here so I won’t go into any great detail in this article. The RDA for protein is set at 0.8 grams per kilogram of bodyweight (g/kgBW), while research typically recommends intakes of 1.2-2.2 g/kgBW for athletic populations (i.e. from endurance to strength athletes). As I mentioned in the protein requirements article, I tend to err on the side of too much than too little protein and typically recommend intakes between 1.7-3 g/kg.BW for most individuals. Such intakes are realistically achievable by most and wouldn’t seem to impede on carbohydrate requirements of athletes for a given energy budget.
3. Setting fat intake
Unlike protein there isn’t really an evidenced-based dosing range to cite when talking about fat intake. As long as essential fatty acid intake is met, which is virtually impossible not to with a typical diet, fat intake technically doesn’t have to be any higher. Having said that, calories have to come from somewhere. Furthermore, in order for a diet not to be bland, in addition to there being enough fat to optimise the absorption of fat soluble vitamins, I like to use intakes of 1-1.5 g/kg as a starting point, which suit both non-athletes and athletes (due to the contribution of intramuscular triglycerides [IMTG] as a fuel source during exercise) alike.
4. Setting carbohydrate intake
Now that we’ve set total kcal, protein and fat, carbohydrates simply fill the remaining calorie allotment. Using myself again as an example, I’ll run through steps 1-4 based on my stats and training/activity.
- REE/BMR = 24.2 x 78 kg = 1888 kcal. Since the “moderately active” activity factor most accurately represents my current activity I’ll multiply my REE/BMR by 1.55 (1888 x 1.55) giving a TEE of 2925 kcal per day.
- Since my athletic goals include maximising muscle hypertrophy and strength, I’ll set protein intake at the upper end (3g/kg of BW) of my recommendations. This equates to a daily protein intake of (78 x 3) 234g. As each gram of protein contains roughly 4 kcal, daily protein intake equates to 936 kcal.
- As I don’t deplete a great deal of IMTG through training, I’ll set fat intake at the lower end of my recommendation (1g/kg). This equates to a daily fat intake of (78 x 1) 78 g. As each gram of fat contains roughly 9 kcal, daily fat intake equates to 702 kcal.
- To calculate carbohydrate intake in grams, all we need to do is subtract the sum of protein and fat kcal from total kcal, then divide by 4 (the amount of kcal per gram of carbohydrate).
- Protein = 234 x 4 kcal/g = 936 kcal
- Fat = 78 x 9 kcal/g = 702 kcal
- TEE (2925 kcal) – 1638 (936 + 702) = 1287 kcal from carbohydrate.
- 1287 / 4 (number of kcal per gram of carbohydrate) = 321 g
Energy: 2925 kcal
Protein: 236 g (32%)
Fat: 78 g (24%)
Carbs: 321 g (44%)
This whole process is pretty straightforward and should take a few minutes at most since all you need to know is your current body weight and training volume/frequency.
From the totals, you will also notice I listed the percentage of total energy that each macronutrient makes up. While knowing this percentage breakdown isn’t all that useful for most purposes, it gives you an idea of how your diet compares to ones that are set up as percentages. In reality, these percentages are not too dissimilar from the Zone Diet. However this won’t be the case for everyone as made in the earlier example.
As a final point on this matter, diet percentages are secondary to meeting a person’s individual macronutrient requirements. In other words, once you’ve worked out how much protein and fat you require, allow carbs fill the remaining calorie budget and let the percentages be what they are. Attempting to do things the other way round is confusing and doesn’t address individual needs.
From the current example, my real-world experience tells me that my maintenance energy need has been overestimated by roughly 200-300 kcal. In this case, I’d leave protein and fat intake the same and decrease the suggested carbohydrate intake from 321 g to roughly 246-271 g per day.
From there, you would split the macronutrients up over a realistic number of meals (3-5) over the course of the day and aim to meet these individual macronutrient goals. It is worth remembering that the total macronutrients consumed is far more important (at least in terms of body composition) than the macronutrient subtype (i.e. type of protein, type of fat, glycaemic index etc.), meal frequency, or any specific timing of the ingested nutrients etc. (with the possible exception of outlandish extremes that are very rarely encountered in the real-world).
Is this for everyone?
As with everything in relation to nutrition, the answer is almost always, “it depends”. These values aren’t set in stone I just use them as a good staring point. I don’t mind going lower than the bottom end of my protein recommendations (e.g. for people who already have achieved their desired amount of lean body mass and are eating at maintenance). However, rarely do I suggest much more than 3 g/kg, even when dieting (a possible exception being drug-fuelled bodybuilders). After accounting for protein, I typically let fat intake determine carbohydrate intake (as it makes up the remaining calories). However, for type II diabetics or insulin resistant individuals, or just people who don’t tolerate carbs very well in general, I like to opt for a lower carbohydrate intake. Because of this, fat intake has to increase in order to make up the calories.
For people who don’t really engage in a great deal of high-intensity exercise, fat intake can also be set a bit higher than recommended above (if preferred), with a relatively lower carbohydrate intake. Contrary to what the insulin-phobic “gurus” would like to convince you, calories do count, and after adequate protein is set, skewing fat or carbohydrate either way will have little overall impact on body composition in healthy individuals as long as total calories remain the same. Anyone who says that you can eat as much as you want as long as you avoid carbs has either completely ignored the available evidence on the matter or/and is trying to sell something.
What about fat loss or muscle gain?
While these recommendations are fine for people who wish to remain weight stable, most people want to lose weight (fat), and some, gain weight (usually muscle). In the case of losing body fat (speaking exclusively about manipulating diet), I like to increase protein slightly (relative to maintenance levels; see my previous article on protein requirements for details on this) and then create an energy deficit as a percentage of maintenance requirements (by roughly 10-20% as a starting point). The reason being that an often quoted 500 kcal deficit would be quite significant for a small female with a maintenance caloric requirement of 1800 kcal (28%), and less so for a large male with a maintenance requirement of 3500 kcal (14%). Calories would be cut from either fat, carbs or both and would depend on several factors (e.g. level of hunger, type of training, food preference etc.). It should also be mentioned that individuals might wish to eat the same and just increase activity, or use a combination of both dieting and increased exercise to bring about fat loss.
In terms of gaining muscle mass, I’d go with the exact opposite (i.e. increase carbs and/or fat) except for keeping protein the same as maintenance levels. Though these recommendations aren't a bad starting point, I should point out that I am grossly oversimplifying matters, and to go in any great detail would take many more articles.
Though total macronutrient intake would seem to have the greatest overall impact compared with any single dietary modification, other variables such as: nutrient timing, meal frequency, macronutrient subtype, nutrient density (vitamin and mineral content per calorie), non-nutritive dietary components and supplementation, would have a measureable impact on body composition, sporting performance and health. That is assuming the ability of an individual to successfully implement a desired macronutrient intake on a daily basis in the first place.
Summary & application
Hopefully these two articles have shed some light on how to properly construct the backbone of a diet (i.e. the macronutrient content) in a simple and individualised manner. Estimating total maintenance macronutrient intake is briefly summarised below and requires knowledge of only current body weight and training load:
- Multiply bodyweight (in kg) by 24.2 (males) or 22 (females) to determine resting energy expenditure.
- Multiply this value by an appropriate activity factor.
- Set protein intake between 1.7-3 g kg of bodyweight.
- Set fat intake between 1-1.5 g kg of bodyweight.
- Let carbohydrate fill the remaining calorie budget.
This totals would then be roughly divided among a realistic number of meals and modified in accordance with real world observations (i.e. changes in body composition) or body composition goals (e.g. fat loss or muscle gain).