Ketogenic Ratio

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The Ketogenic Ratio is the ratio of the weight of fat to carbohydrate and protein in the Ketogenic Diet. So a daily diet that included 200g fat, 10g carbohydrate, and 40g protein would have a Ketogenic Ratio 4:1. While this is a simple concept, there are many factors that make it a little trickier than it appears.

  • A Ketogenic Diet not only specifies the Ketogenic Ratio, but it typically also specifies the maximum amount of carbohydrate, as carbohydrate is far more anti-ketogenic than protein.
  • The Ketogenic Ratio assumes that the total calorie intake matches the ideal intake for age and weight.
    • If fewer calories are taken for weight loss, then the burned body fat needs to be included in the ratio. For example, assume an adult that needs 2,000 calories. If they only consume 100g fat, 10g carbohydrate and 40g protein, the diet provides 1,100 Calories and they burn 900 Calories of body fat (100g). That is a true Ketogenic Ratio of (100+100) to (10+40) or 4:1.
    • It's less clear what happens if more calories are required for exercise. My personal experience suggests extra exercise does not allow for a proportionately greater carbohydrate or protein intake.
  • The carbohydrate intake is measured as Net Carbohydrates, which ignores carbohydrates that are Fiber. (See below for sugar alcohols.)
  • Monounsaturated and polyunsaturated fats tend to produce more Ketones than saturated fat. However, it has been noted that high levels of Omega-6 oil cause Nausea and digestive problems, so Omega-3 and monounsaturated fats may be better.
  • MCT raises Ketone levels directly, even without carbohydrate restriction.
  • The timing of food intake can impact ketone levels. Taking a disproportionate amount of the carbohydrates (or even protein) in a meal can rapidly lower ketone levels.
  • Those with little or no body fat, especially children, may run out of available fat and start to burn muscle, which will drop ketone levels.
  • There are a number of unexpected sources of carbohydrate that can reduce Ketone levels:
    • Carbohydrate can be absorbed via the skin from suntan lotion (sunscreen), lipstick or soap.
    • Toothpaste contains carbohydrate, so it's important not to swallow any while during routine brushing. It may be necessary to rinse with water to wash out any residual toothpaste.
    • Processed foods can contain up to 0.9g carbohydrate per serving while declaring "0g carbohydrate" and other rounding errors can occur. If in doubt stop taking all processed foods to troubleshoot unexpectedly low ketone levels.
    • Medications can contain carbohydrate, especially liquid formulas given to children.
    • IV medication sometimes contains glucose (this is mostly an issue for children being treated for epilepsy with the ketogenic diet).

1 Calculating Macronutrients

calculating how much fat, carbohydrate, and protein is not straightforward. Let's assume you want to do a classic 4:1 ratio ketogenic diet, and restrict your carbohydrate intake to 20 g. If your daily calorie expenditure is 2,000 calories, then the calculation looks like this:

Assume Ratio = 4:1 (grams), 9:1 (calories)
Assume Calories = 2,000
Assume Carbs = 20 grams, 80 calories
Fat Allowance = 90% of 2,000 = 1,800 calories, 200 grams
Protein + Carbs = 10% of 2,000 = 200 calories, 40 grams
Protein = 200 – 80 calories, 120 calories, 30 grams

Using that formula, we can estimate the grams of protein allowed for different calorie requirements and different carbohydrate intakes. Note that the number of calories is an estimate of how many calories you burn, not your calorie intake. If you take in less calories from fat than you burn, your body will burn body fat (after early Ketoadaptation) to make up the difference.

Calories 20g carbs 25g carbs 30g carbs 35g carbs 40g carbs 45g carbs 50g carbs
1,600 35g 34g 33g 31g 30g 29g 28g
1,700 38g 36g 35g 34g 33g 31g 30g
1,800 40g 39g 38g 36g 35g 34g 33g
1,900 43g 41g 40g 39g 38g 36g 35g
2,000 45g 44g 43g 41g 40g 39g 38g
2,100 48g 46g 45g 44g 43g 41g 40g
2,200 50g 49g 48g 46g 45g 44g 43g

2 Sugar Alcohols

Sugar alcohols are generally modified forms of sugar that are harder to digest than regular sugar, therefore they have far fewer calories. On a ketogenic diet, it appears that different sugar alcohols need to be treated differently. I would ignore grams of Erythritol and Lactitol, count half the grams of Xylitol, and all the grams of Maltitol and Sorbitol.

  • Erythritol can be ignored as it's not metabolized at all[1][2]. (It's absorbed but excreted intact.)
  • Lactitol has no impact on blood glucose and only a slight rise in insulin, so it can be mostly ignored[3].
  • Xylitol seems to have some impact on blood glucose, about half that of fructose (glycemic index of 7)[2][3].
  • Maltitol raises blood glucose in larger amounts[4]. 50g of Maltitol raised blood glucose by 75% as much as pure glucose, but 10g had no detectable effect.
  • Sorbitol raises the blood glucose, peaking at about 25% as high as with sucrose (table sugar), but insulin response may be similar[5][6].

3 See Also

4 References

  1. K. Noda, K. Nakayama, T. Oku, Serum glucose and insulin levels and erythritol balance after oral administration of erythritol in healthy subjects., Eur J Clin Nutr, volume 48, issue 4, pages 286-92, Apr 1994, PMID 8039489
  2. 2.0 2.1 Bettina K. Wölnerhanssen, Lucian Cajacob, Nino Keller, Alison Doody, Jens F. Rehfeld, Juergen Drewe, Ralph Peterli, Christoph Beglinger, Anne Christin Meyer-Gerspach, Gut hormone secretion, gastric emptying, and glycemic responses to erythritol and xylitol in lean and obese subjects, American Journal of Physiology - Endocrinology And Metabolism, volume 310, issue 11, 2016, pages E1053–E1061, ISSN 0193-1849, doi 10.1152/ajpendo.00037.2016
  3. 3.0 3.1 SS. Natah, KR. Hussien, JA. Tuominen, VA. Koivisto, Metabolic response to lactitol and xylitol in healthy men., Am J Clin Nutr, volume 65, issue 4, pages 947-50, Apr 1997, PMID 9094877
  4. A. Secchi, A. E. Pontiroli, L. Cammelli, A. Bizzi, M. Cini, G. Pozza, Effects of oral administration of maltitol on plasma glucose, plasma sorbitol, and serum insulin levels in man, Klinische Wochenschrift, volume 64, issue 6, 1986, pages 265–269, ISSN 0023-2173, doi 10.1007/BF01711933
  5. S. Akgün, NH. Ertel, A comparison of carbohydrate metabolism after sucrose, sorbitol, and fructose meals in normal and diabetic subjects., Diabetes Care, volume 3, issue 5, pages 582-5, PMID 7002512
  6. L. Kaspar, K. Irsigler, [A comparison of the blood glucose increase and insulin requirement after oral sucrose, fructose and sorbitol alone or in combination (author's transl)]., Wien Klin Wochenschr, volume 92, issue 19, pages 683-7, Oct 1980, PMID 7008368