http://suppversity.blogspot.com/2014/07/750kcalday-deficit-approach-to-cutting.html

750kcal/day Deficit Approach to "Cutting" Beats Cautious 300kcal/day Deficit: Almost 2kg Fat in 4 Weeks + No Decline in Testosterone or Muscle Loss in Lean Athletes

One of the commonest reasons people don't achieve the physique of their dreams is fear! The fear of losing muscle weight on a "cut" and the fear of gaining fat weight on a "bulk". The study at hand confirms: There is no reason to be afraid of cutting.

In the course of the four-week cutting period in the study at hand, the subjects, 20-35 year-old national and international level Finnish track and field male athletes from jumping and short distance running events (e.g. 100-200m) with already low body fat percentages lost another ~2% body fat, and no muscle in spite of a highly significant 750kcal/day deficit.

The data in Figure 1 which is the outcome of a controlled 4-week study in the course of which the subjects were advised to cut fat and carbs and keep their protein intake stable make a clear statement: Trying to cut with a caloric deficit of only 300kcal/day is a waste of time" ... at least for someone who starts with a body fat percentage of only 10%, as the subjects in the study at hand did.

As you can see in Figure 2 the subjects did as they were told and cut back on both fat and carbohydrates - in conjunction with the physical activity this is certainly the key to lean body mass and performance maintenance.
"The counter-movement jump and 20-m sprint time improved consistently (p ≤ 0.05) only in HWR (-700kcal/day), by 2.6 ą 2.5 cm and 0.04 ą 0.04 s, respectively. Finally, athletes with a fat percentage 10% or over at the baseline were able to preserve FFM." (Huovinen. 2014)
Whether that's also the reason that the scientists did not observe significant differences in serum testosterone in either of the two groups is questionable

(Testosterone / cortisol: 33.6 (pre) vs. 38.3 (post)), though - especially in view of previous results like those I wrote about in the following two articles:
"High or Low Protein Intakes Have Profound Influence on Testosterone, SHBG, Estrogen, Cortisol & Co?" (learn more) and
"High Protein Diets Don't Counter Anti-Anabolic Effects of Low Energy Intake" (learn more)

It's more likely that the 27.1kcal/kg of body weight, the subjects in the 700kcal/day diet consumed were still more than enough to cover the basic energy requirements. With an average body weight of ~75kg that's still more than 2,000kcal and thus way more than the average starvation diet of the average overweight person will deliver.

Bottom line: The results of the study support the use of short, but relatively intense dieting periods. Dieting periods with a 750kcal/day deficit - a deficit that is still only -24% below the baseline intake of the athletes.

What's yet also important is that we don't forget that a dieting principle that works for lean athletes will not necessarily work for an overweight or obese person. The general idea to cut back by 24% and not just 12% (to avoid muscle loss) from carbohydrates and fats while maintaining an optimal protein intake of ~2g/kg body weight is yet something I can whole-heartedly recommend to heavier dieters, as well.