0.4 lb weight loss per day leads to loss of strength and feeling less energetic in lean, active young men
- Executive summary (since this is a long post):Calorie deficit resulting in 0.4 lb weight loss per day leads to loss of strenth (and endurance?) and feeling less energetic in lean, active young (17-35) men over 3 weeksFull post:We tend to assume that our weight loss on trial is all body fat. But, even in the obese individuals who are the subjects of most of the research on calorie restriction (CR), about 25% of weight loss on CR diets will be lean body mass (stuff other than bodyfat, including but not limited to muscle). It is possible in the obese to minimize the loss of skeletal muscle by including exercise (easy for us) and extra protein (not so easy for us).Unfortunately, most of the diet studies are on individuals with lots of spare body fat. For those of us with less to spare, muscle loss appears to be more of a problem, if the small study summarized here ends up being replicated by further research.The lead author was affiliated with the V.A. but an Army researcher (form Natick labs) participated, as did researchers from respected academic institutions including Stanford, Amherst and US Berkeley. Natick has done many studies on dietary needs of soldiers and is a quite respected institution for research like this.The study used lean young men (9 subjects, age 18-35, average weight 170#, average 16% fat in bodyweight), all physically active. Subjects were accepted into the study only if they needed at least 2700 calories per day to maintain a stable body weight. They averaged 3245 in caloric needs per day. Their average, calculated pre-diet Base Metabolism Rate (BMR) for age, weight etc. was 1900 per day.This suggests that the subjects were quite physically active, since the ratio of of 1.7 between total caloric needs and BMR is about the same as I use to calculate my food needs backpacking at 12 miles per day. The Harris-Benedict Equation suggests that a 1.725 ratio between total caloric need and BMR is equivalent to "hard exercise /sports 6-7 days per week".Thus they are not untypical (except for age) from many of us.Each subject was put on a diet that resulted in a 40% reduction in the calories they needed to maintain a steady weight - this averaged a 1300 per day calorie deficit. Significantly, this was accomplished entirely by reducing fats and carbs. Protein levels were maintained very close to the pre-CR baseline. The subjects maintained their usual activity levels.They subjects, not surprisingly, lost an average of 8.4 # in the three weeks of the study, or 0.4 lb per day. This is close to the oft-cited rule of thumb that it takes a 3500 calorie deficit to cause 1# of weight loss. (1300 calories x 21 days divided by 3500 = 7.8)Many people would find this an acceptable weight loss on trail and many who have reported back to this group say they have lost more (up to a lb per day seems not all that uncommon)The weight loss might sound like a benefit, but only 50% of the lost weight in these active, lean individuals was in bodyfat (adipose tissue).The other half of the weight loss was in lean body mass. Negative nitrogen balance was observed, indicating that the body was metabolizing its own protein stores. Over 50% of lean body mass is skeletal muscle, though this does not in itself necessarily indicate that 50% of the total loss came from skeletal muscle, since the body can metabolize things in addition to fat and muscle when it needs to pull calories out of the body. But it is a reason for some concern.Of greater concern: there was a 20% average loss in measured arm strength, statistically significant at the 95% level. The arm strength measure was the only one that isolated strength in the study.On the plus side, aerobic capacity (VO2Max) was preserved.An endurance measure declined modestly (6%) but in this small study did not reach statistical significance.One other performance measured actually improved across the 3 weeks of the test, but the authors suggest that this more complicated test might have shown improved results because the subject simply became more technically proficient at the task, which stimulated loading shells into a field gun (the research was financially supported by money from the DoD as well as from the VA)"Subjectively, participants reported no reduction in their activity levels, but did report that they felt 'less energetic' during exercise of long duration (such as soccer) towards the end of the caloric restriction period."This might be the best single article to read in considering a calorie restricted diet on the trail. The study was small (only 9 subjects) but appears to have been very thorough.To me, it suggests that this level of caloric restriction (e.g. corresponding to a weight loss of a bit under a 1/2 lb per day) is a bad idea at least for those of us who are already pretty lean.Citation:Three weeks of caloric restriction alters protein metabolism in normal-weight, young menA. Brooks, Andrew R. Hoffman and Allen Cymerman Fulco, Steve R. Muza, Paul B. Rock, Gregory C. Henderson, Michael A. Horning, George Anne L. Friedlander, Barry Braun, Margaret Pollack, Jay R. MacDonald, Charles S.Am J Physiol Endocrinol Metab 289:E446-E455, 2005. First Published 3 May 2005;Full copy available as a pdfhttp://ajpendo.physiology.org/content/289/3/E446.full.pdf+htmlJohn Curran Ladd
1616 Castro Street
San Francisco, CA 94114-3707
- Added up our meat... Salmon jerky, beef jerky, beef sticks, bacon jerky, dried buffalo (Tanka), dried ground beef, dried ground pork sausage...
Approx 20 pounds and $400+ for four of us on a 25 day hike plan.
If that isn't enough protein, hopefully the 5 dozen dehydrated eggs will help.
100 person x days of food is a daunting planning task.