12% reduction of what? The basal metabolism? Were the people overeating before? How many calories on average?
"It compared outcomes in a group assigned a target of 25% CR (i.e., a 25% reduction in energy intake below baseline levels) with outcomes in an ad libitum diet control group. "
and
"... CALERIE TM participant requirements included:
Absence of significant health problems, including diabetes, cancer, heart and liver disease, and AIDS
Absence of medication use except oral contraceptives
Age from 20 to 50 (inclusive) for men and ages 20-47 (inclusive) for women
Body mass index (BMI) of 22-27.9 (lean to slightly overweight)
No recent substantial weight loss
No history of eating disorders, behavioral, or psychiatric problems
Use by women of an acceptable form of contraception throughout the study"
If you want to try a tracker out yourself Renoise is great (much cheaper) option for PC/Mac/Linux. There are also several free trackers out there with varying levels of practicality (I only know Polyend and Renoise so I can't really suggest which free ones are good).
There's a bit of a learning curve but once you get the hang of the workflow it's tons of fun!