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Study under review: Effects of eight weeks of time-restricted feeding (16/8) on basal metabolism, maximal strength, body composition, inflammation, and cardiovascular risk factors in resistance-trained males
If you’re reading this article, it’s very likely that you’re fortunate enough to be living in a state of constant food abundance. It’s also quite likely that you rarely go hungry for more than several hours before you’re able to consume pretty much any food that you can imagine. That is, unless you’re one of the increasing numbers of people who practice intermittent fasting (IF).
Fasting can be defined as voluntarily abstaining from food (or certain types of foods) for a specified period of time, for religious or health reasons. A variety of purported health benefits are attributed to IF, which can be in the form of alternate day fasting (ADF; covered in-depth in Study Deep Dives #24, Volume 2), 5/2 dieting (restricting your intake to 500 kcal on two non-consecutive days per week), Ramadan fasting (the Muslim holy month, during which food and drink are consumed only when the sun has set), or time-restricted feeding (TRF; all food is consumed within a set daily time window, which is usually between eight and 12 hours). These concepts have been covered in Study Deep Dives #3 and #13.
As shown in Figure 1, fasting is different from both continuous typical calorie restriction as well as starvation. Calorie restriction features a daily intake of up to 40% below a person’s needs, but with a normal meal frequency. In contrast, starvation refers to chronic and involuntary nutritional deficiency. Health benefits have been observed from both IF and daily calorie restriction, but IF is appealing to many as it can offer a simplified approach for creating a calorie deficit at the end of the day or week. Beyond the simplicity of the approach, it appears that dietary compliance may be improved with IF compared with consistent daily energy restriction.
Among the most-researched forms of IF are Ramadan fasting and ADF. Ramadan fasting is a form of TRF, but beyond that most TRF research has primarily used animal subjects. Despite the lack of research in healthy humans, this practice has been gaining in popularity. Anecdotally, people often assume that IF refers specifically to following a daily eight-hour eating window from noon until 8 p.m., but this is just one form of fasting. Much of the research using TRF in the context of exercise and athletic populations has been in conjunction with Ramadan fasting, and the results have been mixed. Some studies find declines in performance while others have seen no decrements. Beyond Ramadan, a recent study using four-hour TRF windows four days per week found no effects on body composition and no adverse effects on lean mass retention or muscular improvements, after eight weeks of resistance training in previously untrained young men.
In light of the lack of research using the popular noon to 8 p.m. eating window in resistance-trained participants, the study under review was designed to examine the effects of an eight-week calorie-matched TRF protocol on body composition, athletic performance, and metabolic factors during a resistance training program in healthy trained male participants.
Intermittent fasting (IF) is a dietary approach for weight loss and overall health that has been increasing in popularity, but limited research exists on the effects of IF in resistance-trained athletes. This new study looked at the effects of a daily eight-hour eating window in trained males participating in a resistance-training program.
Other Articles in Issue #25 (November 2016)
Interview: Jasmina Aganovic
How much do you know about the bacteria that live on your skin? Whether or not you have skin issues, this interview is worth a look.
Milkshakes and insulin resistance: the perfect storm
There's a lot to be learned about how insulin resistance develops. This highly controlled study tested a saturated fat binge, in order to isolate its effects on glucose levels and insulin resistance.
Starches last for better blood glucose
Advice for blood sugar regulation ranges from "eat a balanced diet" to "beware carbs!". Macros and foods aside, could switching up the order in which you eat the same foods impact blood sugar?
A second look at protein quantity after exercise
Do muscular people require more protein after lifting? How much protein is needed to optimize muscle protein synthesis after a workout? This trial addressed both questions.
New data on vitamin D safety
Vitamin D supplementation would appear to have a pristine safety record, at least at first glance. This meta-analysis takes another look at that issue, specifically at potential effects on excessive calcium levels.
Can probiotics be used to treat multiple sclerosis?
The main supplement that’s been linked to helping MS is vitamin D. This probiotic trial could help inform whether gut microbiome approaches should be equally emphasized.
Interview: Julianne Taylor
Julianne is a New Zealand based nutritionist with a particular interest in autoimmune disease. Here, we pick her brain on what she’s found about the diet-disease connection. Julianne first trained as a registered general and obstetric nurse. She then retrained as a furniture designer, followed by a post-graduate diploma in design for disability in London. Back in NZ in the 1990’s Julianne designed, made, and fitted custom wheelchair seats and other aids for people with extreme physical disabilities.