Maybe A Calorie Is Really Not
A Calorie?
by
Tom McCullough MEd.
George A. Bray, MD; Steven R. Smith, MD; Lilian de
Jonge, PhD; Hui Xie, PhD; Jennifer Rood, PhD; Corby K. Martin,
PhD; Marlene Most, PhD; Courtney Brock, MS, RD; Susan Mancuso,
BSN, RN; Leanne M. Redman, PhD. Effect
of Dietary Protein Content on Weight Gain, Energy Expenditure,
and Body Composition During Overeating. JAMA. 2012;307(1):47-55.
.
ABSTRACT
Objective To evaluate the
effects of overconsumption of low, normal, and high protein diets
on weight gain, energy expenditure, and body composition.
Design, Setting, and Participants
A single-blind, randomized controlled trial of 25 US
healthy, weight-stable male and female volunteers, aged 18 to 35
years with a body mass index between 19 and 30. The first
participant was admitted to the inpatient metabolic unit in June
2005 and the last in October 2007.
Intervention After
consuming a weight-stabilizing diet for 13 to 25 days,
participants were randomized to diets containing 5% of energy from
protein (low protein), 15% (normal protein), or 25% (high
protein), which they were overfed during the last 8 weeks of their
10- to 12-week stay in the inpatient metabolic unit. Compared with
energy intake during the weight stabilization period, the protein
diets provided approximately 40% more energy intake, which
corresponds to 954 kcal/d (95% CI, 884-1022 kcal/d).
Main Outcome Measures Body
composition was measured by dual-energy x-ray absorptiometry
biweekly, resting energy expenditure was measured weekly by
ventilated hood, and total energy expenditure by doubly labeled
water prior to the overeating and weight stabilization periods and
at weeks 7 to 8.
Results Overeating
produced significantly less weight gain in the low protein diet
group (3.16 kg; 95% CI, 1.88-4.44 kg) compared with the normal
protein diet group (6.05 kg; 95% CI, 4.84-7.26 kg) or the high
protein diet group (6.51 kg; 95% CI, 5.23-7.79 kg) (P = .002).
Body fat increased similarly in all 3 protein diet groups and
represented 50% to more than 90% of the excess stored calories.
Resting energy expenditure, total energy expenditure, and body
protein did not increase during overfeeding with the low protein
diet. In contrast, resting energy expenditure (normal protein
diet: 160 kcal/d [95% CI, 102-218 kcal/d]; high protein diet: 227
kcal/d [95% CI, 165-289 kcal/d]) and body protein (lean body mass)
(normal protein diet: 2.87 kg [95% CI, 2.11-3.62 kg]; high protein
diet: 3.18 kg [95% CI, 2.37-3.98 kg]) increased significantly with
the normal and high protein diets.
Conclusions Among persons
living in a controlled setting, calories alone account for the
increase in fat; protein affected energy expenditure and storage
of lean body mass, but not body fat storage.
Figure 1-4.Changes
in Body Weight, Body Fat, and Lean Body Mass During 8 Weeks of
Overeating.
The blue horizontal lines indicate individual participants. The
error bars in the change from baseline graphs indicate 95%
confidence intervals. The amount of energy that the subjects in
the low protein diet group burned remained stable; in the other
two groups the amount rose.
Figure 5.Changes in Resting Energy Expenditure
During 8 Weeks of Overeating.
The blue horizontal lines indicate individual participants. The
error bars in the change from baseline graph indicate 95%
confidence intervals.
Figure 6.Relationship of Energy Intake and
Protein Intake With Change in Body Fat and Change in Lean Body
Mass
A higher protein intake resulted in more lean body mass build up,
and did not correlate with the growth in fat mass.
In this study 25 healthy, 16 weight-stable males and 9 females aged
18 to 35 years, with a BMI between 19 and 30, were recruited.
Researchers wanted to find out if overeating a low or high protein
diet would produce less weight gain than overeating a normal protein
diet. All the food was provided and participants resided in a
metabolic unit for 10 to 12 weeks with no prescribed or regular
exercise program. Alcohol and caffeine were prohibited throughout
the study and smokers were excluded.
The researchers divided the subjects into three groups. The low
protein diet group were given The low protein diet had 6% of energy
from protein, 52% from fat, and 42% from carbohydrates. The normal
protein diet group got 15% of energy from protein, 44% from fat, and
41% from carbohydrates. The high protein group got 26% of energy
from protein, 33% from fat, and 41% from carbohydrates.
The researchers determined how many calories a day we needed for
each individual to keep their weight stable. After the subjects
reached weight stability they were given 954 calories a day more
than they burned for eight weeks.
At the end of the 8 weeks it first appeared that the low protein
group had done best. This group had 'only' put on 3.6 kg. The normal
protein diet subjects had put on 6.1 kg and the high protein diet
subjects had put on 6.5 kg. The subjects in the low-protein diet
group had lost 0.7 kg of body weight; the subjects in the normal
protein diet group had gained 3.2 kg and the subjects in the high
protein diet group had gained 4.0 kg. Once researchers looked in to
body composition they found the as protein increased, lean body mass
also increased as part of the weight gain. Explaining the weight
gains.
The key finding of this study is that calories are more important
than protein while consuming excess amounts of energy with respect
to increases in body fat. Calories alone, however, contributed to
the increase in body fat. In contrast, protein contributed to the
changes in energy expenditure and lean body mass, but not to the
increase in body fat.
Amazingly enough, the subjects in this study did no exercise. Had
they been participating in weight training, the results no doubt
would have been even better.
