Update: The Latest on Caffeine, Exercise, Fat & Weight Loss - Increased Performance, Energy Expenditure (6%) & Fatty Acid Oxidation (27%) vs. Decreased Sleep Quality & Burnout
|We love coffee! There is not doubt about it 85% of the Americans consume coffee on a daily basis and it's not much different for the rest of the West (Mitchell. 2013).|
With 54.2 mg of caffeine per floz and thus ~ 400mg per cup "having a Deathwish" would bring an average male athlete with a body weight of 80kg right to the 5mg/kg body weight maximum that has been used in the majority of high(er) dose caffeine supplementation trials.
You can learn more about coffee at the SuppVersity
A possible reduction in testosterone is yet not the only downside you have to consider. A recent study from the University of Sydney, which is the first new study in today's "Caffeine Update", for example, found that the ergogenic benefit of consuming caffeine containing carbohydrate beverages (aka energy drink) during your workouts comes at a price: deleterious effects on sleep (Miller. 2014).
|Figure 1: Plasma caffeine concentration before, during and at the end of exercise, and 30 min before bedtime (n = 5). Mean ± SD; Caffeine ingestion, bedtime (Miller. 2014)|
|Table 1: Sleep indices after caffeine or placebo ingestion (Miller. 2014)|
|Figure 2: Previous studies report significantly reduced melatonin production in response to "only" 5 cups of 130 mg/cup caffeine coffees per day for one week vs. the same amount of decaff (Shilo. 2002)|
"But caffeine is so good!?"
What do you say? "Caffeine is so good"? Yes, it is. I mean, caffeine in fact "so good". In Miller's study, it lead to improved time trial times during cycling in all subjects (even the anxious and nauseous ones; caffeine 19.7 ± 3.3; placebo 20.5 ± 3.5 min; p = 0.006), while reducing the rates of perceived exertion (caffeine 12.0 ± 0.6; placebo 12.9 ± 0.7; p = 0.004) and heart rate (caffeine 175 ± 6; placebo 167 ± 11 bpm; p = 0.085).
Surprising benefits for type II diabetics: In spite of the fact that the contemporary evidence clearly indicates that a regular moderate to high caffeine consumption protects against type II diabetes (-29% risk; Jiang. 2014), even scientists question, whether caffeine is still beneficial, whence you're already diabetic. A recent study from the Midwest State University of Parana does now suggest that at least the small minority of type II diabetics who work out, can benefit from the glucose reducing effects of pre-workout caffeine supplementation. With a 65% reduction and 75mg/dl (p < 0.05), the allegedly high amount of 1.5mg/kg caffeine lead to a highly significant reduction in plasma glucose in the eight diabetic subjects (age 55±10 years) who worked out at only at 40% heart rate (HR) reserve for 40 min at the facilities of the Science Postgraduate Program (daSilva. 2014).This is yet not the only good news scientists have come up with since the last SuppVersity caffeine review. Researchers from the School of Allied Health Sciences at the Griffith University in Australia (Schubert. 2014), for example, report that "combining caffeine with exercise creates a greater acute energy deficit" and could thus provide the foundation to increased weight loss / reduced weight gain in both lean and overweight individuals.
Is caffeine the agent that keeps you lean?
The subjects in the study at hand were required to be non-smoking and non-obese (BMI < 30 kg/m²), pre-menopausal (women), between 18 and 45 years of age and not on any medicine known to influence lipid, carbohydrate, or caffeine metabolism (except oral contraceptives). They were not allowed to be dieting and had had to be weight stable in the previous 3 months (± 5 % by self-report), Moreover, they were free of any cardiovascular or metabolic diseases and otherwise healthy.
We're not dealing with caffeine naive individuals! In view of the fact that the central nervous system effects which are in turn highly relevant for the influence of caffeine on energy expenditure and fatty acid oxidation, it's important to point out that the subjects were not caffeine naive. Both, the 6 men and 8 women who participated in the study at hand had a habitual caffeine consumption of 206 ± 194 mg per day.To make sure that the individual dietary preferences of the subjects would not mess up the results, participants were asked to complete a food diary and record all food and drink. Additionally, all participants were also asked to refrain from strenuous exercise the 18 hours before their trial to which they had to come after an overnight fast and without breakfast. When they arrived at the lab, the subjects received 3mg/kg body weight with 250ml of water. Afterwards they had to sit quietly before the resting energy expenditure (REE) was measured continuously for the final 20 min of a 60 minute rest period.
|Figure 3: Overview of the allegedly somewhat complicated, but realistic and thus relevant exp. setup (Schubert. 2014)|
As complicated as it may seem, the study protocol is actually not unrealistic
At +150 min (30 min post-exercise/rest), participants were given another 3 mg/kg body weight dose of caffeine or placebo along with a small liquid calorie meal (250 mL, 825 kJ, 30.3 g carbohydrate, 3.8 g fat, 8.3 g protein; Up N Go®, Sanitarium Health & Well-Being™; Australia). This beverage was provided to provide participants with a small amount of calories and examine post-prandial responses during all trials over the final 90 min. As the researchers point out, ...
"[...t]he rationale for dividing the caffeine dosage was threefold. First, 3 mg/kg BM has been shown to improve exercise performance to the same degree as larger doses (Desbrow. 2012). Second, by using multiple doses several hours apart, typical patterns of caffeine/coffee consumption are mirrored (i.e. early and mid-morning coffee). A recent study reported that coffee consumption peaks in the morning (0600-0800) with a second peak late morning (1000-1200), with a decline thereafter during the week (Gibson. 2013). The third reason was to maintain plasma caffeine levels in order to examination their relationship to other variables." (Schubert. 2014)Aside from the fact that the average US adult probably won't consume more than 200 mg and thus ~40mg less caffeine than the male study participants (average body weight 81kg) of the study at hand with one cup of coffee, Schubert et al. have thus created a pretty realistic scenario the exercise component of which matches the situation of the average pre-workout consumer pretty well.
|Figure 4: Changes in total energy expenditure (EE), fatty acid and carbohydrate / glucose oxidation in response to the 2x1.5g/kg body weight caffeine consumption in healthy men and women during and after exercise (Schubert. 2014)|
Burning more fatty acids ≠ losing more fat!
|Figure 5: It's not popular to say this, but it's true: Whether you gain or lose weight depends on your relative energy intake and the latter was negative for both exercise groups in the study at hand (Schubert. 2014)|
If we don't care about weight, but fat loss, however, the increase in fatty oxidation during the workout may matter, yet again. In contrast to the oxidation of fatty acids during the workout, the restoration of muscle and liver glycogen will eventually not necessarily happen in the absence of amino acid and thus possibly (!) muscle breakdown. A fact that leaves the "caffeine doped" athlete at a two-fold advantage: (1) Increased overall energy expenditure and (2) a decreased risk of lean mass loss.
|Figure 6: Energy expenditure (kcal) from CHO and FAT over the whole 4h study period (Schubert. 2014)|
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