Ketogenic Diet & Obesity
Weight Loss Study Aim
To evaluate the efficacy and metabolic impact of a high-protein, low-carbohydrate,
low-fat ketogenic diet (K diet) in the treatment of morbidly obese adolescents
with initial weights of >200 percent of ideal body weight. Six adolescents,
aged 12 to 15 years, weighing an average of 147.8 kg (range, 120.6-198.6
kg) and having an average body mass index of 50.9 kg/m (39.8-63.0 kg/m),
consumed the K diet for 8 weeks. Daily intake consisted of 650 to 725
calories, which was substantively in the form of protein (80-100 g). The
diet was very low in carbohydrates (25 g) and fat (25 g). This was followed
by 12 weeks of the K diet plus two carbohydrates (30 g) per meal (K+2
diet). Anthropometric data and blood and urine were collected at enrollment,
during week 1, and at 4-week intervals throughout the course of the study.
Resting energy expenditure was measured by indirect calorimetry. Body
composition was estimated using dual-energy x-ray absorptiometry, bioelectrical
impedance analysis, and urinary creatinine excretion at enrollment and
on completion of each phase of the diet. Nocturnal polysomnography and
multiple sleep latency testing were conducted at baseline and repeated
after an average weight loss of 18.7 kg to determine sleep architecture,
frequency and duration of apneas, and daytime sleepiness.
Weight Loss Study Results
Subjects lost 15.4 +/- 1.4 kg during the K diet and an additional 2.3
+/- 2.9 kg during the K+2 diet. Body mass index decreased 5.6 +/- 0.6
kg/m(2) during the K diet and an additional 1.1 +/- 1.1 kg/m(2) during
the K+2 diet. Body composition studies indicated that weight was lost
equally from all areas of the body and was predominantly fat. Lean body
mass was not significantly affected. Weight loss was accompanied by a
reduction in resting energy expenditure of 5.2 +/- 1.8 kcal/kg of fat-free
mass per day. Blood chemistries remained normal throughout the study and
included a decrease in serum cholesterol from 162 +/- 12 to 121 +/- 8
mg/dL in the initial 4 weeks of the K diet. An increase in calcium excretion
was accompanied by a decrease in total-body bone mineral content. A paucity
of rapid eye movement sleep and excessive slow-wave sleep were seen in
all subjects at enrollment. Weight loss led to an increase in rapid eye
movement sleep and a decrease in slow-wave sleep to near normal levels.
Weight Loss Study Conclusions
The K diet can be used effectively for rapid weight loss in adolescents
with morbid obesity. Loss in lean body mass is blunted, blood chemistries
remain normal, and sleep abnormalities significantly decrease with weight
loss.
Source: Willi SM, Oexmann MJ, Wright NM,
Collop NA, Key LL Jr. Department of Pediatrics, Medical University of
South Carolina, Charleston 29425, USA. 1998
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