Main Menu              Health Library           Losing Weight with Life Ahead          Some Popular Diets          

 DIET CARBOHYDRATE and LOSS of WEIGHT

Abstract:  Research now confirms from consistent results on six recent independent studies and from relevant direct comparisons in a large meta analysis that a low carbohydrate diet subtracts more weight from those dieting than does an average or low fat diet.  Dieters lost about twice as much weight from low carbohydrate diets as from low fat or average diets of similar calorie amounts.  Calorie fuel values have suggested that a pound of weight will be added or subtracted for each 3500 added or subtracted dietary calories.  These actual results suggest  that carbohydrates require about 2500  diet calories to produce a pound of body weight, but that it requires about 4500 diet calories of average fats plus proteins to produce a pound of body weight.  The theory that all diet calories contribute equally to weight gain or loss appears invalid. No information on the relative contribution to body weight of diet calories of proteins per se was found

This advantage in rate of weight loss in no way endorses all low carbohydrate diets as healthful, and Life Ahead analyzes diet health separately. Life Ahead now includes a unique new weight change indicator that recognizes the combination of both diet calories and amounts of carbohydrate to weight gain or loss.  An important implication of this is that most of the recent increase in obesity of our population must be due to increases in the eating of carbohydrates.

Background:   A major health problem in the US and other industrialized world populations today is the great increase in obesity and overweight of our populations.  People simply are gaining weight by eating more and eating too much.  Yet despite vast publicity, much research, and millions of diet books a solution of this problem remains elusive.  Most people find dieting difficult, obtain inadequate reduction in body weight, and later regain most weight lost.  A near sacred tenet of nutritionists and academic health researchers has been: Losing weight simply requires the eating of a lesser amount of calories.  The total amount of calories of foods eaten  determines weight loss.  The type and kind of foods eaten are not relevant, it is only calories in foods that matter.  

This theory that derives from calorie values and energy probably has not been rigorously demonstrated and may be dogma. The theory has been challenged since the mid 1800's by individuals claiming that diets low in carbohydrates will produce faster than usual weight loss.  An important proponent of this has been Dr. R.C. Atkins who advocated from both research and experience in his weight loss clinic that diets very low in carbohydrates of a given amount of calories will produce faster loss of weight.  But Atkin's diet that is high in fats is indicated to be unhealthful from a majority of related research and has been strongly opposed by most academic researchers.  Other doctors that operated weight loss clinics also have proposed diets lower than usual in carbohydrates (i.e. Scarsdale, Protein Power, Zone, etc) for faster weight loss.  Although proponents of low carbohydrate argue that their diets are "Not unhealthy", this remains controversial. 

Key questions argued vigorously now are:  (1)  Does a low carbohydrate diet really provide faster weight loss than does a diet low in fats and of usual high content of carbohydrates;  and (2)  Can a very low carbohydrate diet that must by balance include higher amounts of fat, protein, or both be healthy?  

A Life Ahead Contribution:  With regard to (2) above, Life Ahead provides a unique method for valuing the long range health of individuals from cardiovascular diseases and cancer - the key diseases that today usually determine longevity - from an objective analysis of all available research found.   This method shows that health from diet depends on the multiple and probably causative results of up to 23 different nutrients included in each food, and not just one factor such as carbohydrate or fat per se. Further health effects of any long range diet depend also on the other risks of each individual to specific life terminating diseases, and that a best diet for each can vary widely.  Finally, Life Ahead provides a quantification of potential benefits that can be compared with such potential benefits as weight loss and dietary enjoyment.  

Although saturated fats and trans fats contribute as harmful, mono unsaturated fats appear near benign and polyunsaturated fats are usually beneficial to health. Protein is not now implicated as harmful to either cardiovascular diseases or cancer, and its potential  harm to most people when present in larger amounts is being disputed.  Thus it is possible that healthful  low carbohydrate diets can be devised that can be supported by present research.  

But an answer to question (1) above also is needed:  Do low carbohydrate diets really produce faster weight loss than do low fat diets?

Weight Loss, Low Carbohydrate and Low Fat  Diets:  Atkins cited 10 early studies showing that low carbohydrate diet produce faster weight loss than do low fat high carbohydrate diets.  He also cites experience from 25,000 people helped via weight loss programs in his large clinic. Authors of other diet books that also managed weight loss clinics also have found that low carbohydrate diets hasten weight loss.  This conclusion has been disputed by various panels of opposing academic experts.  And until recently insufficient  convincing research may have been available on this subject.  Study 7 in  Table 2 following attempted to segregate more than a hundred studies of weight loss from differing diets.  But most studies did not concisely compare low carbohydrate diets and low fat diets of the same calorie amount on a given population.  And information on many of these studies was incomplete. 

Fortunately a few useful direct studies have been found published in the past seven years.  Results of these are included in Table 2.   A conclusion from these comparisons is both unanimous and clear:  Low carbohydrate (Carbo) diets DO reduce weight of obese men and women not only faster but can reduce it much faster than do low fat (F+P)diets  Study #1 of Samaha found a 13.3 pound loss in 26 weeks on the low Carbo diet vs only 4.4 pounds on the low fat diet.  Study #2 of Westman although not a comparison, obtained a 20.7 pound average loss in the same time from a low Carbo diet with no calorie restriction. This is impressive.  Study #3  of Foster found 2 to 2 1/2 times higher loss of weight on the low Carbo diet than on the low fat diet.  Study #6 of Brehn also found a much larger loss in weight from the low Carbo diet vs. a restricted low fat diet.  These results usually were statistically significant.

The results from studies #4 and #5 are of interest for two reasons.  First they included diets of the same calories for both low Carbo and low fat groups.  And second they included diets differing in amounts of 35% vs 57% and 25% vs. 45% of carbohydrates in total calories. These are much higher amounts than the 10-15% amounts of Carbo advocated by Atkins, but are in the range advocated by some other low Carbo diet proponents.  Although the advantage for the lower Carbo diets was less than that for studies of very low Carbo diets, the lower of these moderately high Carbo diets still produced a higher weight loss.  This suggests that carbohydrates per se of a given calorie amount contribute significantly more to weight gain than do the other macro nutrients of fats and protein. 

The only useful result derived from Study #7 arguably was the direct comparison of weight loss from studies that involved similar amounts of diet calories.  The direct comparison of all Carbo diets of less than 1500 calories per day showed a very large average loss of 40 pounds for 18 low Carbo diets vs. only a 3.1 pound average loss for all 129 a higher Carbo diets.  Diets of more than 1500 calories which in many cases would not be expected to produce much weight loss also confirmed a higher weight loss from the low Carbo diets.  The authors' attempt to derive a useful statistical result from all included diets including those not comparable in diet calories was predictably unsuccessful.  

Thus the available evidence to date supports adequately the probable fact that low Carbo diets substantially increase loss in weight. First, all direct studies 1 through 6 show this as a consistent finding for all periods of dieting.  Second is the practical experience of several doctors that managed actual weight loss clinics on many thousands of participants.  Third, the diets comparable in calories included in Study #7 show a striking advantage in weight loss for the low Carbo diets below 1500 calories per day that would be the key diets involved in weight loss research.  Agreement of at least three objective and useful direct studies is accepted as adequate in Life Ahead for action by health-interested persons.  The available evidence on weight loss of low Carbo diets substantially exceeds this requirement.

Actual adherence to diets was noted as poor by some researchers.  Most consistent results were obtained at 13 weeks of dieting that is still is quite a long time for the full adherence of most people.  Weight loss tended to lessen and even reverse for the much longer diet periods, and near peaked at about 26 weeks, suggesting declining adherence to the regimes wanted as time advanced.   Thus the potential weight loss of those that adhered completely to the diets provided should have been significantly higher than the actual average values obtained in Table 1, especially for the longer periods of dieting.

The Mechanism:  The mechanism by which carbohydrates contribute to weight has been widely publicized and verified.  The digestion of excess carbohydrates produces sugars that can stimulate excess insulin production that in turn converts part of the sugars to stored body fat. The fact that carbohydrates contribute selectively to weight loss suggests that the dogma that "All food calories are equal both in producing energy and body fat"  cannot be true.  In retrospect, this calorie theory should have been long suspect from basic chemistry and engineering.  Fuels of given calorie value produce widely differing actual energy output in differing environments such as a furnace, or in an engine.  Energy efficiency values can vary from 30% to above 95%, and differing fuels such as gas, oil, gasoline, or diesel fuel produce differing energy output efficiencies in a given environment. The biochemical processes by which fats, proteins and carbohydrates are converted to energy differ vastly.  And these conversions take place in different organs of the body and produce differing waste products.  The likelihood is remote that such complex and differing chemical processes could be exactly equivalent in energy conversion efficiency. And the likelihood that equal input calories of differing nutrient chemicals would convert to identical amounts of body fat or weight becomes even more remote.

Carbo Contributes Differently than F+P to Weight Gain or Loss:  Results in Table 2 provide a basis for estimating the relationship of calories of Carbo and F+P to change in body weight. The approach used was to find the combination of Carbo and F + P values consistent with 3500 calories per pound from an average diet (assumed as 50% Carbo and 50% F+P) that would best explain the actual research results obtained. The analysis suggested that Carbo requires about  2500 calories to add a pound of weight - and that F+P requires about 4500 calories to add a pound of body weight.  Use of these values in a model now used in Life Ahead produced forecast values of weight loss noted in the following Table  1. For purpose of these computations reducing diets were assumed to included 500 fewer calories per day than usual diets.

                                                       Table 1

   Weight Loss assuming Carbo @ 2500 Cal/lb, F+P @ 4500 Cal/lb

Study No   Actual Weight Loss   Calculated Weight Loss

       Low vs. Higher Carbo,lbs  Low vs.Higher Carbo,lbs 

   1      13.3 vs 4.4 @26 wks      41.5 vs. 25.5             

   2             20.7                  22.9 

   3      13.6 vs 5.4 @13 wks      20.9 vs. 12.7             

   4      12.9 vs.9.9 @ 13 wks     17.0 vs. 12.7          

   5      23.5 vs.16.3 @ 12 wks    17.6 vs 13.9                     

   6      19.6 vs. 11.0 @ 13 wks   21.8 vs. 14.2           

Except for Study #1, most calculated results are in rough agreement with what could be expected from the actual results. The weight loss in study #2 of 20.7 for diets of similar calories is close the the forecast loss of 22.9 lbs for the period of dieting.   Actual weight loss was moderately less than those computed for studies 3,4, and 5, and this is expected as dietary compliance probably would have been less than 100%.  Actual weight loss in 26 weeks was only 20% above that at 13 weeks, and this and probable poor compliance may explain the much lesser than expected weight loss in Study #1.  Values of 2000 Calories per lb for Carbo and 5000 per lb for F+P may provide a slightly more accurate computed weight loss ratios for Carbo vs. F+P, and the proposed values of 2500 and 4500 per pound of weight probably represent conservative differences of valuation.

The Life Ahead Diet Analysis:  This available research and analysis should convince the health-interested person that weight can be reduced faster and and from fewer calories of deprivation with a low Carbo diet. And disturbingly, weight also should increase much faster with a high Carbo diet!  Atkins and the several related diet book authors are confirmed as correct on this claim.  But this in no way confirms that such diets will be adequately healthy.  The very low Carbo Atkins diet of very high fat probably will increase cancer risk substantially even if cholesterol can be maintained.  But Life Ahead provides the tools for designing low Carbo diets that should involve a minimum of risk, and can provide quantitative valuations of added  risk that individuals can use.  As a general guide, diets that will produce measurable differences in longevity must be maintained for long periods of time.  A short term effort to reduce weight via a diet somewhat higher than usual in risk maintained only for a few months probably will have little health debit if is replaced long term by a healthful diet.

A Life Ahead Weight Indicator Recognizes both Diet Calories and Diet Carbo:  Life Ahead now includes as an aide to dieters a weight loss and gain indicator that now is believed to be unique.  The program first computes a probable normal calorie amount that will on average maintain weight for persons of any height, weight, age, and sex. When calories in the entered diet exceed a modest amount per day, a difference in daily and inferred difference in weekly diet calories vs. this normal amount is identified as each dietary food is entered into the program.  The Weight Change Indicator then computes from this difference in calories and from amounts of Carbo and F+P in the diet the weight gain or loss that this entered diet will produce per week for an average US man or woman. This method recognizes and computes automatically the selective effect of Carbo calories on weight.  Thus as each food is entered into a diet the indicator will suggest a weekly weight loss or gain from foods entered to this time.  Users thus can develop diets that should reach at meet an approximate goal in producing  long range potential weight loss.  And the health value of any developed diet can be immediately computed by the program.

It has been pointed out that the part of carbohydrates that is fiber does not contribute to the insulin related weight gains obtained from other types of carbohydrates.  Accepting this, Life Ahead removes dietary fiber from its computation of Carbo related weight.  This correction also is made to the indicator showing total Carbo grams entered up to this time.

Users should recognize these weight loss estimates as a rough guide.  First, people have differing metabolisms, and some will require less and others will require more calories than average for weight maintenance.  Thus some will lose more and others will lose less than the presently computed amounts.  Second, the estimates assume that the diet entered at the point of food entry will be exactly maintained for future periods of time.  And third, low Carbo diets usually will result in more than expected weight loss during a first week or two because they produce selective loss of body water.  Thus short term loss of weight should be larger the forecast for an initial period of low Carbo dieting. Finally note that the actual weight loss obtained in the real-world diet programs in Table 2 averaged only about one pound per week, with a maximum loss of 2 pounds per week over longer time, and these were losses obtained by mostly quite obese people.  Health interested persons should be wary of dietary claims of far larger rates of weight loss than this from any diet program.