Is the Anabolic Diet really anabolic?
In the mid-1990s, before the Atkins craze blew up, some bodybuilders were already experimenting with the Cyclical Ketogenic Diet (CKD). This eating plan was introduced to the strength training world by accomplished powerlifter and physician Mauro Di Pasquale, via his book The Anabolic Diet, and the late Dan Duchaine, who wrote about it in his tome BODYOPUS.
A CKD involves 5-6 days of very low-carbohydrate eating (the ketogenic phase) followed by 1-2 days of a very high-carbohydrate intake, repeating the cycle on a weekly basis.
The premise behind the CKD was that the body would accelerate fat burning during the low-carb days, then replenish muscle glycogen stores during the brief high-carb phase.
By way of adjusting caloric intake, it could be used for cutting or for bulking.
So while the original CKD strategy didn't promote the "calories don't count" nonsense, it still embraced the now-disproved belief that carbohydrate restriction per se increased fat loss, while carbohydrate intake promoted fat gain. The two-day high-carb period, we were told, allowed for muscle glycogen replenishment but was not long enough for the alleged fat-depositing effects of carbs to kick in.
We were also told the diet would increase growth hormone levels (hence the "Anabolic" tag). The erroneous belief that low-carbohydrate diets increase growth hormone output was based on the observation that experimental episodes of hypoglycemia (low blood sugar) can be accompanied by increased GH output. The simplistic assumption was that low-carb diets lower blood sugar, so therefore they must raise GH levels.
The assumption was not just simplistic, but wrong. No-one has shown an isocaloric ketogenic diet to cause greater GH output. To trigger GH release, researchers must first give subjects a large dose of glucose that causes initial hyperglycemia (high blood sugar), followed a few hours later by hypoglycemia. It should be noted that hypoglycemia is not a good state to be in. If your diet consistently leaves you hypoglycemic, then your diet sucks.
The initial hyperglycemia in these experiments is accompanied by suppressed GH levels, but three to five hours after the initial bolus of glucose, the subsequent hypoglycemia of these subjects is accompanied by a rise in GH.
Obviously, gulping down large amounts of glucose every 5 hours in the hopes of boosting GH has nothing to do with a low-carbohydrate diet.
Basically, Cyclic Ketogenic diets were built upon a false premise. For the record, I'm not belittling Dr Di Pasquale or Duchaine; the former by all accounts is a sincere and highly knowledgeable individual, the latter was often described as a "mad scientist" who reveled in experimenting with diet, supplements and, infamously, drugs.
Despite its flawed theoretical foundations, the CKD has its devoted followers. Those who understand that strict ketogenic dieting is flawed, but still can't shake off their anti-carb conditioning, believe (hope) there is something special about eating keto during the week, then carb-loading on the weekends.
But is there?
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Finally, a Clinical Trial
While researchers had previously examined the effects of brief bouts of low-carb eating followed by a single carb-load phase, no-one to my knowledge had ever performed a longer-term study comparing a CKD with a balanced mixed diet.
That changed in 2020, when a group of Czech researchers recruited 25 healthy young males with at least one year of resistance training experience. They randomized the lads to follow either a CKD (n = 13) or a balanced mixed diet (n = 12) for 8 weeks.
Irrespective of dietary assignment, energy intake was individually tailored to provide a daily 500-calorie deficit for each subject.
The CKD involved consuming less than 50 grams of carbohydrate daily, from Monday through Friday. Protein intake was set at 1.6 g/kg daily, with the remainder of calories coming from fat. On the weekends, the CKD subjects consumed 15% protein, 15% fat, and 70% carbohydrate.
The balanced diet group, meanwhile, was instructed to consume a macronutrient ratio of 15% protein, 30% fat, 55% carbohydrate on a daily basis.
All participants performed three strength workouts and three aerobic workouts per week.
The strength program was a three-way split (chest, thighs, upper back) with workouts lasting around 60 minutes.
The aerobic workouts comprised a 30-minute run, with heart rate around 130–140 beats/minute.
This was a free-living study, so overall adherence to diet was checked once weekly by a nutritionist. Furthermore, adherence to the CKD was evaluated through urinary ketone measurements performed twice daily and by measurement of blood β-hydroxybutyrate at the end of the study.
So what happened?
The Results
β-hydroxy-butyrate significantly increased in the CKD group while remaining unaffected in the balanced diet group.
Both diets produced similar reductions in body weight, body fat mass and BMI.
Average lean body mass and body water content was reduced by the CKD, but not the mixed diet. Looking at the individual results, six of the balanced diet subjects experienced some degree of lean mass increase, compared to only two in the CKD group.
After eight weeks, the CKD group experienced little-to-no strength improvement on their 1RM bench press, lat pulldown, and leg press.
The balanced diet group experienced greater improvements on all three, with statistically significant improvements recorded for the lat pulldown and leg press.
Unlike the CKD group, the mixed diet group experienced increases in peak workload, peak oxygen uptake/kg, peak workload/kg, and physical working capacity at a heart rate of 170/min after the eight-week intervention.
So after eight weeks, both diets produced similar weight losses. But in the CKD group, the drop of body weight was due to a combination of decreased body fat, body water, and a slight, but statistically significant, decline in lean body mass. On the contrary, in the balanced diet group neither body water nor lean body mass were significantly affected and the weight reduction was predominantly due to body fat loss.
There was no anabolic effect of the CKD. The best that could be said is that the slight decrease in lean body mass in the CKD group did not impair 1RM strength.
In contrast to low-carb propaganda, an increased reliance on fat oxidation did not help endurance performance. Again, only the mixed diet group experienced improvement in endurance parameters.
As the researchers concluded, "Our study thus demonstrates that the cyclical ketogenic reduction diet effectively reduces body weight but is not an effective strategy to increase anaerobic or strength performance in healthy young men."
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