Is the thermic effect of food higher if you are lean?

Is the thermic effect of food higher if you are lean?
By Fredrik Tonstad Vårvik 

The thermic effect of food (TEF) is the increase in energy expenditure in response to the digestion, absorption and storage of food (1,2). In this article, I explore whether or not the thermic effect of food is higher in leaner individuals.

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The thermic effect of food: the research

Protein is the macronutrient that increases your metabolism the most. True. Protein has a thermic effect of 20-30%, whereas carbs are at 5-15% and fat is at 3-4% (3,4). Since meals rarely contain only one macronutrient, mixed meals are often given a TEF of around 10% (1,2).

If two subjects – one having a normal and the other having a subnormal thermogenic response to a meal – increase their food intake, the former will not put on as much weight as the latter (5). Some studies show differences between obese and lean subjects. Most of the research indicates that lean individuals have a higher TEF than obese individuals, both for mixed meals (5–12), and for fat (5), while other studies have found no difference (13–15).

A review by Jonge and Bray in 1997 included 49 studies. About 60% of the studies found a higher TEF in lean subjects compared to obese subjects (16). A newer review by Granata and Brandon from 2002 came to almost the same conclusions: out of 50 studies, 60% found a higher TEF in lean subjects compared to obese subjects (1).

Tataranni et al, who conducted a study in a respiratory chamber concluded that body weight has no association with TEF (2). Worth mentioning here is that the mean fat percentage for the subjects was about 30%±10 for male and above 40%±10 for female, which means there were very few lean (if any?) subjects participating in the study. However, Tataranni et al associates insulin resistance with lower TEF, which has a stronger association with obesity in the literature. This table from Swaminathan 1985 shows the TEF of a mixed meal between the different macronutrients between obese and lean individuals (5). In this study, as we can see, a mixed meal in lean subjects is high, actually higher than the TEF of protein alone, 25% vs 22.5%, respectively.

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Numbers up to 30-35% TEF have been reported for protein (4,17). However, since carbs and fat are needed in addition to protein, we most often eat a mixed meal. Therefore, it appears that if you are lean, you can’t get much benefit from increasing your protein, if it is sufficient in the first place.

Let’s take a look at Antonio et al’s two recent studies, where the very high-protein groups had 3.4g/kg/d and 4.4g/kg/d (18,19). In these two studies, there was no difference in improvements in body composition in the 4.4g/kg/d group vs low-protein group, and there were small improvements in body composition in the 3.4g/kg/d group compared to the low-protein group. More precisely, fat percentage decreased by 1.8% more in the 3.4g/kg/d group compared to the low-protein group. This can be explained by a higher adherence to training compared to the lower-protein group, a higher NEAT from the high-protein group (20), or over/under-reporting from dietary recall. Another important point; in the 4.4g/kg/d study, the dropout was high and some of the subjects stated that it was too difficult to consume the high-protein diet. In the 3.4g/kg/d study there was also a higher dropout in the high-protein group, however, the dropout in both studies can be partially explained by a higher number of participants in the high-protein groups. That said, the researchers divided the participants in two unequal groups to take into account the loss of subjects from potential lack of compliance in the high-protein group. So, why follow a diet that you can’t adhere to in the first place anyway? Protein and satiety will be an article for later.

Protein intake in bodybuilders has been noted up to 4.3g/kg (21) however, it is doubtful whether they gained any benefits from it. It may have even been counterproductive, due to the decrease in both fat and carbs, which can have an impact on hormones, vitamins, performance, recovery, etc. If you are obese it may seem like a good idea to follow a diet with a relatively high-protein intake, since the mixed meal in this study only had a TEF of 10%, vs protein of 18.7%.

Why are there conflicting studies?

As we can see, the studies appear to be conflicting, but why is this so? First, methodological factors such as meal size and composition, palatability and timing, measurements <3 hours, short duration, measurement and equipment, environmental factors, and heterogeneity in human obesity may explain different findings (1,2,9). Granata and Brandon mention that in both Jonge and Bray’s review as well as their own, most of the studies with measurements <3 hours reported that TEF was lower in obese individuals, while the minority of studies with measurements >3 hours reported lower TEF in obese individuals (1).

Most studies use variable caloric loads that are dosed after bodyweight or fat-free-mass (FFM), while some use the same caloric load for all subjects. There are problem with both, however, which makes it difficult to compare and conclude. The magnitude of the TEF is strongly related to the size of the caloric load. Thus, when meal sizes are dosed relative to bodyweight or FFM, obese subjects receive larger meals which may bias the comparison to the lean subject. On the other hand, if both receive a given quantity of nutrients, TEF may increase less in obese subjects because their rest metabolic rate (RMR) is higher (15). However, this was not the case when both lean and obese subjects were eating meals with 35% of their RMR (9). Jonge and Bray’s review speculates that factors such as BMI were used and not body fat percentages, that some studies didn’t leave a large enough gap between the upper limit of the lean group and the lower limit of the obese group (16). This could lead to an overlap in the percentage of body fat and thus misclassification between the two groups, which again could lower the chance of finding a potential effect of TEF in different body fat sizes.

If obese people have a lower thermic effect of food, why?

Recent studies suggest that blunted TEF in obese people is related to impaired glucose tolerance and insulin resistance(9,16). From Jonge and Bray’s review, the greater the degree of insulin resistance and body fat, the lower TEF. The same researchers also speculate that lower sympathetic nervous system and higher age could be part of it. Granata and Brandon seem to agree that higher age reduces TEF but believe the sympathetic nervous system theory is more speculative (1). A reduced rate of non-oxidative glucose storage is believed to play a role, which has greater energy cost than glucose oxidation (9). Other explanations that are mentioned are a reduced thermogenesis in brown adipose tissue and skeletal muscle. Tateranni et al also mention lower spontaneous physical activity among the people with lower TEF (2). Another suggestion is that obese people may have reduced sensitivity to the actions of thermogenic hormones that are stimulated with a meal. One reason for this can be because of a sedentary lifestyle (22), as shown in the figure.

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As you can see in the figure, if you are sedentary, you don’t have as good of satiety signaling as if you are active. Regarding the insulin resistance, it has been shown that a reduction in insulin sensitivity down regulates nervous system activity in the postprandial phase, and reduces energy expenditure (23).

If supposed lower TEF in obese individuals is true, the researchers don’t seem to agree if it is part of a consequence of obesity or if it contributes to obesity (1).

Practical applications:

  • If you are lean, you may have a TEF of up to 25% for a mixed meal, based on one study. However, since the research is far from clear – you should opt for 10-25% in your calculations, as the research slightly favors a higher TEF in lean subjects. So maybe, just maybe, you can enjoy an extra scoop of ice cream without bad conscience if you are lean.
  • If you are obese, you should remain on the safe side and assume you have a lower TEF than lean individuals. Opt for a TEF up to 10%.

From the data available, it is clear that we need much more controlled research in this area.

References

  1. Granata GP, Brandon LJ. The thermic effect of food and obesity: discrepant results and methodological variations. Nutr Rev. 2002 Aug;60(8):223–33.
  2. Tataranni PA, Larson DE, Snitker S, Ravussin E. Thermic effect of food in humans: methods and results from use of a respiratory chamber. Am J Clin Nutr. 1995 May 1;61(5):1013–9.
  3. Jéquier E. Pathways to obesity. Int J Obes Relat Metab Disord J Int Assoc Study Obes [Internet]. 2002 Sep;26 Suppl 2. Available from: http://dx.doi.org/10.1038/sj.ijo.0802123
  4. Halton TL, Hu FB. The effects of high protein diets on thermogenesis, satiety and weight loss: a critical review. J Am Coll Nutr. 2004 Oct;23(5):373–85.
  5. R Swaminathan RFK. Thermic effect of feeding carbohydrate, fat, protein and mixed meal in lean and obese subjects. Am J Clin Nutr. 1985;42(2):177–81.
  6. Tappy L. Thermic effect of food and sympathetic nervous system activity in humans. Reprod Nutr Dev. 1996;36(4):391–7.
  7. Dabbech M, Boulier A, Apfelbaum M, Aubert R. Thermic effect of meal and fat mass in lean and obese men. Nutr Res. 1996 Jul 1;16(7):1133–41.
  8. Schutz Y, Bessard T, Jéquier E. Diet-induced thermogenesis measured over a whole day in obese and nonobese women. Am J Clin Nutr. 1984 Sep;40(3):542–52.
  9. Segal KR, Edaño A, Blando L, Pi-Sunyer FX. Comparison of thermic effects of constant and relative caloric loads in lean and obese men. Am J Clin Nutr. 1990 Jan;51(1):14–21.
  10. Segal KR, Edaño A, Tomas MB. Thermic effect of a meal over 3 and 6 hours in lean and obese men. Metabolism. 1990 Sep;39(9):985–92.
  11. Segal KR, Gutin B, Nyman AM, Pi-Sunyer FX. Thermic effect of food at rest, during exercise, and after exercise in lean and obese men of similar body weight. J Clin Invest. 1985 Sep;76(3):1107–12.
  12. Segal KR, Gutin B, Albu J, Pi-Sunyer FX. Thermic effects of food and exercise in lean and obese men of similar lean body mass. Am J Physiol. 1987 Jan;252(1 Pt 1):E110–7.
  13. Blundell JE, Cooling J, King NA. Differences in postprandial responses to fat and carbohydrate loads in habitual high and low fat consumers (phenotypes). Br J Nutr. 2002 Aug;88(2):125–32.
  14. Segal KR, Gutin B. Thermic effects of food and exercise in lean and obese women. Metabolism. 1983 Jun;32(6):581–9.
  15. D’Alessio DA, Kavle EC, Mozzoli MA, Smalley KJ, Polansky M, Kendrick ZV, et al. Thermic effect of food in lean and obese men. J Clin Invest. 1988 Jun;81(6):1781–9.
  16. de Jonge L, Bray GA. The thermic effect of food and obesity: a critical review. Obes Res. 1997 Nov;5(6):622–31.
  17. Binns A, Gray M, Di Brezzo R. Thermic effect of food, exercise, and total energy expenditure in active females. J Sci Med Sport Sports Med Aust. 2015 Mar;18(2):204–8.
  18. Antonio J, Ellerbroek A, Silver T, Orris S, Scheiner M, Gonzalez A, et al. A high protein diet (3.4 g/kg/d) combined with a heavy resistance training program improves body composition in healthy trained men and women – a follow-up investigation. J Int Soc Sports Nutr. 2015 Oct 20;12(1):39.
  19. Antonio J, Peacock CA, Ellerbroek A, Fromhoff B, Silver T. The effects of consuming a high protein diet (4.4 g/kg/d) on body composition in resistance-trained individuals. J Int Soc Sports Nutr. 2014 May 12;11(1):19.
  20. Bray GA, Smith SR, de Jonge L, Xie H, Rood J, Martin CK, et al. Effect of dietary protein content on weight gain, energy expenditure, and body composition during overeating: a randomized controlled trial. JAMA J Am Med Assoc. 2012 Jan 4;307(1):47–55.
  21. Spendlove J, Mitchell L, Gifford J, Hackett D, Slater G, Cobley S, et al. Dietary Intake of Competitive Bodybuilders. Sports Med Auckl NZ. 2015 Apr 30;
  22. Blundell JE, Gibbons C, Caudwell P, Finlayson G, Hopkins M. Appetite control and energy balance: impact of exercise. Obes Rev Off J Int Assoc Study Obes. 2015 Feb;16 Suppl 1:67–76.
  23. Watanabe T, Nomura M, Nakayasu K, Kawano T, Ito S, Nakaya Y. Relationships between thermic effect of food, insulin resistance and autonomic nervous activity. J Med Investig JMI. 2006 Feb;53(1-2):153–8.

About the author

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Fredrik Tonstad Vårvik is a personal trainer & nutritionist. He writes articles and work with online coaching at FredFitology. Follow him and his colleagues at Facebook & Twitter. Check out FredFitology for more info.

A Larger Muscle is a Stronger Muscle Due to Increased Strength and Leverage

Bret’s Intro: I’m very excited about the publication of our recent article. The three of us (Andrew Vigotsky, Chris Beardsley, and yours truly) have devoted a large percentage of our studies over the past few years to biomechanics, and although it’s not always sexy, it’s very important for fully understanding various concepts in strength & conditioning. 

Many of us strength coaches devoured the works of Mel Siff, Vladimir Zatsiorsky, and Yuri Verkhoshansky in hopes of gaining insight to better equip us as practitioners. While much of their work was esoteric and over the heads of the majority of strength coaches, every once in a while we gleaned some useful information. I believe that the information in our article, although esoteric, is indeed useful, especially pertaining to powerlifting and athletics. What is fascinating is that increased muscle moment arms are definitely beneficial for strength and high force activities, but for power and high speed activities, they can actually be counterproductive (we explained this in the full article). 

This publication would not have been possible had it not been for Andrew Vigotsky’s superior drive, passion, curiosity, and mathematics background. I can think up concepts but I lack the mathematical skills to model and validate them. Huge props to Andrew for his diligence and talent!

Cliff Notes: As a muscle grows larger, it can produce more torque (rotational force) through greater linear force created by the muscle, but also through greater leverage about the joint center, and the leverage improves by approximately the square root of the increase in the muscle’s cross-sectional area. 

Biomechanically, how does hypertrophy increase strength?
By Andrew Vigotsky

Two years ago, while helping construct the Biomechanics of the Squat and Deadlift manual for Bret’s 2×4: Maximum Strength product, Bret explained to me that increasing a muscle’s size will increase its moment arm. He and Chris Beardsley illustrated this relationship in their Hip Extension Torque manual, but although it made intuitive sense, there were no published studies modeling this relationship. While concepts are neat and useful, it is important in science to construct models to explain mathematical relationships and validate the concepts.

We recently decided to develop this model and submit it to PeerJ for publishing. The model was accepted and published today. It’s open-access so you can download the full paper HERE. The model describes the relationship between a muscle’s size (anatomical cross-sectional area) and its leverage (moment arm length).

* Click HERE to Download the Full PDF *

First, I think it’s important that the readers understand what, exactly, a moment arm is, and why it matters for strength. As you know, the body is made of bones that rotate about joints. Muscles and external forces “fight” one another to rotate the joint. The forces that have a tendency to rotate a joint are classically called torques, or moments. Torques or moments equal the force applied to the bone times the moment arm, or perpendicular distance of that force to the axis of rotation (see below). With regards to a muscle, the larger the moment it can produce, the stronger you are.

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When muscles increase in size, the amount of force they can produce also increases – this is well known and accepted. Obviously a larger muscle will be able to produce more force than a much smaller muscle. However, the other component to generating a moment, a muscle’s moment arm length, has not been well studied. It has been shown that they are correlated (Akagi et al. 2012; Sugisaki et al. 2010), and one study even showed that, with a 33.6% increase in triceps brachii anatomical cross-sectional area, the triceps brachii moment arm increases by 5.5% (Sugisaki et al. 2014).

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In order to gain a better understanding of this relationship, my colleagues – Bret Contreras and Chris Beardsley – and I developed a model of the biceps brachii and brachialis, wherein the original size of the muscles were atrophied to one-half their original size and hypertrophied to two times their original size. We were able to calculate the new moment arm lengths, and how the new moment arm affected each muscle’s tendency to flex the elbow (joint moment contribution, or torque that each muscle produces). Our main findings can be found in Table 1, below.

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This is a relatively unexplored area of biomechanics and hypertrophy that may be important to consider. Not only does the muscle produce more force, but also, depending on the muscle and joint angle, its mechanical advantage will change. We have included an infographic below that summarizes our study and findings.

11_15_Vigotsky_xs

References

Akagi R, Iwanuma S, Hashizume S, Kanehisa H, Yanai T, and Kawakami Y. 2012. In vivo measurements of moment arm lengths of three elbow flexors at rest and during isometric contractions. Journal of Applied Biomechanics 28:63-69.

Sugisaki N, Wakahara T, Miyamoto N, Murata K, Kanehisa H, Kawakami Y, and Fukunaga T. 2010. Influence of muscle anatomical cross-sectional area on the moment arm length of the triceps brachii muscle at the elbow joint. Journal of Biomechanics. 10.1016/j.jbiomech.2010.06.013

Sugisaki N, Wakahara T, Murata K, Miyamoto N, Kawakami Y, Kanehisa H, and Fukunaga T. 2014. Influence of Muscle Hypertrophy on the Moment Arm of the Triceps Brachii Muscle. Journal of Applied Biomechanics. 10.1123/jab.2014-0126

December Strength & Conditioning Research Questions

Every month, Chris and I write the monthly S&C Research review service. Subscribe, and you will learn about the 50 most important sports science studies published every month. If you haven’t signed up yet, I think you should. It is such a great amount of information for only $10/month, and the feedback we’ve received so far is phenomenal.

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You can subscribe HERE or just try it by buying a back issue HERE.


Strength & conditioning, power and hypertrophy

  1. Is sprint running the best way to train to improve sprint ability?
  2. What sled loads are best for resisted sled sprint training?
  3. Can an in-season training program improve sprint ability in soccer players?
  4. How does concurrent training frequency affect a range of physical qualities?
  5. Does rest interval length affect the number of repetitions performed in supersets?
  6. How is aerobic capacity related to CrossFit workout performance?
  7. Does creatine enhance gains from plyometric training in female soccer players?
  8. Does altering training frequency by menstrual phases affect gains in untrained females?
  9. Does altering training frequency by menstrual phases affect gains in trained females?
  10. How does strength change across the menstrual cycle?
  11. Does training to failure lead to greater gains in strength than training not to failure?
  12. Are forced repetitions effective for muscular hypertrophy?

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Biomechanics & motor control

  1. How should the term “power” be used in exercise science research?
  2. Is the force–velocity relationship linear in the bench press?
  3. Can we measure the PAP effect at multiple points in time post-conditioning contraction?
  4. What factors affect the PAP effect on jumping, sprinting, and throwing performances?
  5. How does a gluteal activation protocol affect sprint running performance?
  6. Which hip abduction and external rotation exercises produce the highest gluteal EMG activity?
  7. How does knowledge of load affect RFD and power output?
  8. How do joint angle movements differ between jump and drop landings?
  9. How does EMG activity of shoulder, trunk, and arm muscles differ between push-up variants?
  10. How do peripheral and central fatigue contribute to repeated cycling sprints?

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Anatomy, physiology & nutrition

  1. Is whey protein effective for increasing lean body mass in resistance-trained individuals?
  2. Are there benefits of a higher protein diet (3.4g per kg of bodyweight)?
  3. Does higher protein intake conserve lean body mass in older adults during weight loss?
  4. Does protein supplementation affect intramuscular anabolic signaling?
  5. Are low-fat or low-carb diets best for overweight and obese adults?
  6. Do ketogenic diets lead to losses in lean body mass?
  7. Do macros affect metabolic adaptions during weight loss?
  8. Can catching up on sleep help reduce the adverse effects of sleep restriction?
  9. Does sleep restriction lead to increased energy intake?
  10. Can melatonin supplementation improve body composition?
  11. Do changes in myonuclear domain size occur during resistance training?
  12. Is HIIT better than steady state exercise for fat loss?
  13. Is HIIT better than steady state exercise for brain health?
  14. Is HIIT better than steady state exercise for appetite regulation?
  15. Do food- and exercise-induced energy deficits produce the same compensatory energy intake?

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Physical therapy & rehabilitation

  1. Does cold water immersion help adolescent athletes recover?
  2. Does cold water immersion speed HRV recovery post-exercise?
  3. Does foam rolling work by altering stretch tolerance?
  4. Can foam rolling added to a stretching program improve gains in flexibility?
  5. Does bodyweight affect eccentric knee flexor strength in the Nordic hamstring curl?
  6. Should tendon rehabilitation involve interventions to improve motor control?
  7. Is there evidence for central sensitization in tendinopathy?
  8. Can visual feedback during drop landing training reduce knee valgus?
  9. Does contracting the pelvic floor muscles affect active lung capacity?
  10. Can pelvic floor muscle training improve active lung capacity?
  11. Can strength exercises added to a stretching program help treat plantar fasciitis?
  12. Does stretching one joint improve flexibility at other joints?
  13. Does greater foot pronation lead to more anterior pelvic tilt?

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December Strength & Conditioning Research Preview: High Intensity Interval Training (HIIT) for Fat Loss Edition

Every month, Chris and I write the monthly S&C Research review service. Subscribe, and you will learn about the 50 most important sports science studies published every month, covering strength & conditioning, biomechanics, anatomy & physiology, and sports medicine.

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You can subscribe HERE or just try it by buying a back issue HERE.

Here is a preview of the December 2015 edition, which covers a wide range of research but has a special theme of High Intensity Interval Training (HIIT) for fat loss!

How do we assess HIIT for fat loss?

Over much of the last 20 years, HIIT has been championed by many as the most effective type of exercise for fat loss. Recently, there has been a backlash, and some fitness writers are now arguing that HIIT is less effective than steady state (SS) exercise. When the New Year arrives, and people start trying to lose the weight they have gained over the holiday season, you can bet there will be a lot of discussion on the topic.

So who is right?

To find the answer, we first need to define our question scientifically. Then we can do a literature search for the right studies to help us answer it. We can use the PICO (population, intervention, comparator, outcome) mnemonic to make sure we don’t miss any key features of the studies we need, like this:

  • Population – healthy adults, either lean or overweight
  • Intervention – an HIIT exercise program, lasting several weeks
  • Comparator – a SS exercise program, of the same duration
  • Outcome – changes in bodyweight and body fat

From our PICO analysis, we can see that we need long-term studies with at least two training groups (one HIIT and one SS) in which the researchers measure bodyweight (using a scale) and body fat (by DEXA, skinfolds, bioelectrical impedance or Bod Pod) at the beginning and end of the intervention. Then, by comparing the results of the two groups, we can see whether HIIT or SS exercise is better for fat loss.

If HIIT does prove to be better, despite typically using less energy in each workout and therefore over the whole exercise program, then we might ask ourselves how this might be happening, but that would be another question!

What about excess post-exercise oxygen consumption (EPOC)?

When researchers uncover a result they do not understand (like HIIT being similarly or more effective than SS exercise for fat loss despite involving less energy expenditure), they propose mechanisms for what might be producing these strange effects (like greater EPOC in HIIT compared to SS exercise). Sometimes, they guess correctly but, more often than not, their initial guesses are wide of the mark.

This is totally normal.

For example, at the moment, researchers are still trying to figure out whether the apparently superior (or more accurately – apparently more efficient) effects of HIIT over SS exercise are produced by differences in EPOC, reductions in appetite, increased fat oxidation, greater increases in lean body mass, or greater exercise adherence. Various groups are testing hypotheses in these areas, looking for what might be the underlying cause of the effects seen in long-term studies.

cardio

Often, one mechanism suddenly receives a lot of attention and is discounted by some groups, as EPOC has been recently. For those of us who enjoy reading research, this is fun, as we can tick off that possibility and narrow down the field of what might be the real cause of the effects. But for assessing whether HIIT or SS exercise are better for fat loss, studies about mechanisms are not that relevant.

Why not?

Studies about mechanisms (like those telling us about the size of the EPOC energy expended during HIIT) only help us understand how an effect is happening, not whether it happens. Even if EPOC is discounted as a mechanism for the (potentially) superior effects of HIIT exercise, the effect could be produced by a different mechanism.

Which is more efficient for weight loss, SS exercise or HIIT?

The study: High-intensity interval training and isocaloric moderate-intensity continuous training result in similar improvements in body composition and fitness in obese individuals, by Martins, Kazakova, Ludviksen, Mehus, Wisloff, Kulseng & King, in International Journal of Sport Nutrition and Exercise Metabolism (2015)

What did the researchers do?

The researchers compared the effects of long-term programs of HIIT and moderate-intensity continuous training (MICT) involving similar energy expenditure (EE) (as well as an HIIT program that involved half of the EE) on changes in bodyweight, changes in body composition (using dual energy X-Ray absorptiometry (DEXA) scanning), improvements in cardiovascular fitness (as measured by an incremental VO2-max test on an indoor cycle ergometer), alterations in resting metabolism rate (RMR) (as measured using indirect calorimetry), non-exercise activity thermogenesis (NEAT) levels (as measured by actigraphy, using a uniaxial accelerometer monitor) and insulin sensitivity (as measured by taking blood glucose measurements and using the Homeostasis Model Assessment (HOMA) approach) in sedentary obese individuals.

All subjects exercised 3 times per week for 12 weeks on a cycle ergometer. They were asked to maintain their normal diet throughout the program. The full HIIT program involved workouts comprising 8 seconds of sprinting (as hard as possible) and 12 seconds of recovery for as many repetitions to induce EE of 250kcal per workout. The half HIIT program was similar but aimed to induce EE of 125kcal per workout. The MICT involved exercising at 70% of maximum heart rate for 250kcal of EE.

What happened?

The researchers observed a significant reduction in bodyweight in the full HIIT (-1.3kg), half HIIT (-1.8kg) and MICT (0.8kg) groups but there was no significant difference between groups. They observed significant reductions in both trunk and leg fat mass and found significant increases in both trunk and leg lean body mass in all groups. However, there was no significant difference between groups for any outcome. They concluded that full HIIT, half HIIT and MICT training programs all produced similar reductions in bodyweight, and improvements in body composition.

sprint2

Do HIIT or SS exercise affect appetite regulation?

The study: Effects of high-intensity intermittent exercise training on appetite regulation, by Sim, Wallman, Fairchild & Guelfi, in Medicine & Science in Sports & Exercise (2015)

What did the researchers do?

The researchers compared the effects of long-term supervised exercise HIIT and MICT on body composition (as measured by dual-energy x-ray absorptiometry [DEXA]), cardiovascular fitness (as measured by VO2-max in an incremental cycle ergometer test) appetite regulation (as measured by energy intake (EI) at a test meal consumed after high and low energy pre-load drinks), free-living EI over the course of a single day (as measured by self-recorded food diary), free-living physical activity over the course of a single day (as measured by accelerometry), perceptions of appetite (using a visual analog scale (VAS) to assess fullness, hunger, satiation, desire to eat, and prospective food consumption), appetite-related hormones (including the appetite-stimulating hormone ghrelin, the satiety hormone leptin, insulin, pancreatic peptide (PP) and peptide tyrosine tyrosine (PYY), as measured by blood samples) and insulin sensitivity (as measured by the homeostatic model assessment (HOMA-IR) index) in the fasted and fed states and in sedentary, overweight males.

The training groups trained 3 times per week for 12 weeks, with each workout lasting 30 – 45 minutes. The HIIT workout comprised intervals of 15 seconds at 170% of VO2-max and 60 seconds at 32% of VO2-max. The MICT group exercised at 60% of VO2-max. Work done was matched between groups.

What happened?

The researchers found no significant changes in bodyweight or fat mass in either group. They also found no effect on appetite regulation in either HIIT or MICT groups, as measured either using EI following pre-load drinks or using free-living EI over the course of a single day. There was a non-significant trend for EI post-intervention to be reduced to a greater extent in the HIIT group than in the MICT and control groups. Leptin was significantly reduced in HIIT only and ghrelin was unchanged in all groups.


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