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Low Carb/High Protein Diets

Are low carb/high protein diets healthy? The answer in a nutshell is yes. But to clarify a point and to state it categorically, you cannot successfully engage in this type of diet while maintaining a low fat eating pattern. It is impossible and impractical!

Herein lies one of the perceived problems/issues that many have with this diet. For years, we have been warned of eating fat with tales of gloom, doom, obesity and heart disease. With good reason, I may add. The eating of fat with carbohydrates present in the diet will result in almost complete storage of the dietary fat as adipose tissue and eventual presence of the associated health problems. However, consumption of fat without the presence of carbohydrate does not end up with the same result.

Let me state here and now that when I refer to carbohydrates, I am specifically referring to starches and sugars and that would include most fruit. The fibrous type vegetables do not elicit the same hormonal (insulin) responses and therefore are an integral part of a low carbohydrate diet.

The basic issue is the presence of insulin combined with a correlated lack of the antagonistic hormone, glucagon. When insulin is present the body will not, cannot and does not use fat as fuel (dietary or stored). Also, while insulin is present, the body is fantastically primed to store fuel, not burn it. While carbohydrates are being consumed, that is all that the body will use as fuel.

Insulin and glucagon are essentially hormones that control fuel storage and usage, respectively. The other factor determining fuel usage is directly related to the amount of that particular fuel that is consumed. Simply, if you consume greater amounts of carbohydrate, your body will switch to almost exclusive usage of that fuel, becoming set up to store the other sources of energy (fat, protein and alcohol) as fat. It also sets the body up to spare (not use) fat, glucose and protein as energy sources. The body will decrease/increase its use of glucose in direct proportion to the amount of carbohydrate being consumed. Simply put, the more of it you eat, the less your body will depend on other substances (fat) for energy. By correlation, when you eat less carbohydrate, your body will simply shift to other fuel sources (fat) for energy.

The principle behind a low carbohydrate diet is simple: deny the body its preferred source of fuel (carbs), and it has to manufacture fuel from other sources. This is called "gluconeogenesis" and is the formation of sugar from non-sugar sources. Simply, if you do it right, then you set your body up to access its fat stores for energy. (Nirvana!)

The body can manufacture glucose from body tissues such as protein and fat. Glucose can also be manufactured from dietary protein. In fact, up to 58 percent of consumed protein will be converted to glucose, provided the protein intake is sufficient. However, a smaller elevation of insulin will occur than that experienced with the consumption of carbohydrates. 

To make a diet like this work, to prevent muscle loss through protein breakdown and to sustain an isocaloric food intake, the calories have to come from somewhere! If carbohydrate is limited to between 10 and 100 grams as it should be, then the balance of your calories must come from protein and fat.

Incidentally, the timing of the carbohydrate consumption is often a point for discussion, with much of the opinion weighed on the “before midday” bandwagon. Realistically, it makes little difference when the carbs are eaten. It is probably more beneficial to eat them as the last meal at night or immediately after the p.m. workout, when glycogen stores are at their lowest and any insulin response will result in replenishment of glycogen rather than fuelling your energy requirements and inhibiting gluconeogenesis.

Protein consumption has been the subject of much debate over the last 20+ years, and the criteria has changed like Melbourne weather. Very recent research indicates that "ideal protein consumption" figures have been grossly inadequate (the health fears associated with high intakes are unfounded), based on “manipulated study results” and ridiculously overstated.

Minimum intake of protein should be approximately 1gm/lb (.45gm) bodyweight and, where the bodyweight is less than 150 pounds, then a minimum intake of 150 grams should be consumed to prevent muscle loss during low carbohydrate dieting. With the addition of exercise, especially heavy/intense type, up to 3gms/lb of bodyweight is not unheard of. Anecdotally, my intake of protein (past and present) and that of the thousands of national and international class bodybuilders that I know personally or have met in my 15 years at the highest level of sport regularly exceeds the 3gm/lb mark. I find it interesting that the pro high protein "noise" tends to come from the strongest, most muscular humans on the planet and the low protein lobby is essentially advocated by individuals who are mostly of a significantly less muscular bearing! (Stimulates some thought?)

If one works the grams back to calories, even at a relatively high protein intake of 1.5gms/lb for a 175lb (80kg) individual, that would give a total number of calories from protein (262.5gms x 4) of 1,050 (values are approximate and do change from journal to journal and from protein source to protein source.). Combine that with an intake of 50 grams of carbohydrate, and you get a daily calorie consumption of 1,250 calories. Hardly a sustainable amount for anyone, nevermind an 80 kilogram, hard training male. However, the consumption of good quality protein, such as lean beef, invariably involves the consumption of fat. To get 262.5 grams of protein, one would have to consume about 1.3 kilograms of meat (I use meat as an example; the protein of course can come from a variety of animal and even plant sources.), which on average contains 6gm/100gm of fat, which in turn computes to around an extra 700 calories. This brings the individual daily calorie intake to 1950 calories, somewhat more sustainable but still possibly too low.

The choice then remains that in order to increase calories, one must increase the protein and/or fat content of the diet. In order to minimize the insulin level in the blood (due to the glucose conversion rate of protein), it is advisable that the extra calories come from fat sources (i.e., oils, avocados, etc.) or the consumption of higher fat meats.

Before you all start jumping up and down about health and cholesterol, there are numerous studies now available that show blood lipid profiles, triglycerides and HDL/LDL fractions improving significantly on this type of diet. This article is too compressed to list them all. I apologize for this, but the publications listed below have most of them. To make a statement claiming that research in this field is inadequate or does not exist is downright misleading and points to a distinctly narrow minded “selective reading” mentality.

Much of the criticism of the low carbohydrate diet has been at its level of calories. Any apparent successes achieved were reported to be due to the fact that it is invariably low calorie and the fat loss occurred due to this reason and not the adjustment of macronutrients. In many cases, I have to agree. However, this fact stems from the fear of consuming fats. As I stated at the outset of this article and in the previous few paragraphs, one cannot successfully engage in long-term low carbohydrate combined with low fat dieting.

As a rough guide, maintaining a calorie deficit of 500 calories per day (using exercise and food restriction) would be ideal. Sedentary individuals can calculate on 10 cals/lb of body weight, moderately active individuals on 12 to 15 cals/lb and very active people on around 18 cals/lb. This is of course approximate and is not set in concrete, but it is a good starting point.

This debate will rage for a while yet. Despite what is claimed, this type of eating is not a “fad diet.” It has been around far longer than the low fat/high carbohydrate diet has and will continue to be popular as long as results are being achieved and maintained.

If you are totally happy with the way you look, feel and perform and you are the proud consumer of either a high carb or low carb diet, then good for you. But if you are unhappy with the way you look, feel or perform, then change what you are doing – now! (“If nothing changes then nothing changes”). Over 65 percent of Australians are classified as clinically fat! The low fat/high carb diet is failing for many. We need to consider other options – and soon. Get these minds open.


  1. The Ketogenic Diet – Lyle McDonald. ISBN: 0-9671456-0-0 Morris Publishing. (This book has over 600 very relevant, peer reviewed references in it pertaining to low carbohydrate dieting and is absolutely essential reading for the dieter or practitioner).
  2. Textbook of Medical Physiology – Arthur C. Guyton. W. B. Saunders 1996.
  3. Flatt J. P. ‘Use & storage of carbohydrate & fat’. Am J Clin Nutr (1995) 61(suppl): 952S-959S.
  4. Flatt J. P. McCollum Award Lecture, 1995: ‘Diet, lifestyle & weight maintenance’. Am J Clin Nutr (1995) 62: 820-836.
  5. Schrauwen P. et. al. ‘Role of glycogen-lowering exercise in the change of fat oxidation in response to a high fat diet.’ Am J Physiol. (1997) 273: E623-E629.
  6. Schrauwen P. et. al. ‘Fat balance in obese subjects: Role of glycogen stores.’ Am J Physiol. (1998) 274 E1027-E1033.
  7. Flatt J. P. ‘Integration of the overall response to exercise’. Int J Obesity (1995) 19 (suppl): S31-S40.
  8. Jungas R. L. et. al. ‘Quantitative analysis of amino acid oxidation and related gluconeogenesis in humans.’ Phys Rev (1992) 72: 419-448.
  9. ‘Lemon, P. ‘Is increased dietary protein necessary or beneficial for individuals with a physically active lifestyle?’ Nutrition Reviews, 1996, 54: S169-S175.
  10. Bell J. et. al. ‘Ketosis, weight loss, uric acid and nitrogen balance in obese women fed single nutrients at low caloric levels’. Metab Clin Exp (1969) 18: 193-208.
  11. Bistrian B. R. et. al. ‘Effect of a protein sparing diet and brief fast on nitrogen metabolism in mildly obese subjects’. J Lab Med (1977) 89: 1030-1035.
  12. Diabetics General -DISPATCH - ENDO 99: Diabetics Improve Health with Very High-Fat, Low-Carb Diet’. By Cameron Johnston, Special to DG News, San Diego, CA -- June 15, 1999.
  13. Nutrition Almanac, 3rd Edition, Lavon J. Dunne. Nutrition Search, Inc.