Before You Start a Low-Carb Diet

Preparing to Go Low-Carb

measuring your waist
It's a good idea to do some measuring before starting a new diet. Amanada Rohde/E+/Getty Images

Before starting on any new eating program, it's important to do two things: 1) make sure you're prepared for what's ahead, and 2) take some measurements before you start, so you can know what changed.

Preparation to Change Your Way of Eating

Changing what you eat can be daunting, and most people don't succeed in making the adjustment to a different way of eating. Without preparation and support, the odds are not in your favor.

Think carefully about whether you are motivated to do this, and make sure you have support. Then, do the steps in this Guide to Getting Started and check out How to Get Through the First Week. Make sure you have the types of foods you'll need. You can find help here:

Things to Measure

I can't tell you the number of people who have regretted not taking measurements before starting on a new way of eating. Ideally, you would get some blood tests done as well as measuring things you can do at home. For example, if six months from now you find out your cholesterol numbers, you'll want to know if they have changed in a good or bad direction. These are things that commonly change on a low-carb diet:

Weight - Weigh yourself on a scale you'll have regular access to, and weigh yourself at the same time of day each time.

Also, calculate your BMI, as it can be useful to track this as well.

Body Fat Percentage - We talk about "losing weight", but what we really want to lose is fat. Ideally, you'll find out your body fat percentage before starting out. Here is more information about body fat percentage, as well as some methods for tracking it, including one you can do with no special equipment (just a scale and tape measure).

(Note: BMI and body fat percentage are not the same thing.)

Waist and Hip Circumference - Even more important (healthwise) than overall fat is so-called "visceral fat" or "abdominal fat" - the fat that is around our organs and in our livers. A rough measure of this can be found by measuring your waist. If you waist is greater than 35 inches (88 cm) for a woman or 40 inches (102 cm) for a man, you probably have excess visceral fat. However, taller people may want to check their waist/hip ratio. Divide your waist circumference by your hip circumference. You are looking for a ratio of .7 or less for a woman, and .9 or less for a man. Also, for people whose BMI is over 35, waist circumference or waist/hip ratio does not tend to be as reliable a predictor of health problems.

Blood Pressure - Blood pressure often responds quickly to a low-carb diet. If your blood pressure is high, you might want to track your blood pressure at home. (If you are taking blood pressure medication, be sure to tell your doctor about your diet, as it's very common for the amount of medication you need to change.)

Blood Glucose - Your blood glucose after meals will be lower if you eat significantly less carbohydrate, and your fasting blood glucose may change as well.

If you are diabetic, you will surely want to monitor this. (Consider doing this is you are prediabetic as well.) If you are taking medication for blood sugar, inform your doctor of your diet change (see medication link in the previous paragraph).

Blood Lipids (Cholesterol and Triglycerides) - You can expect HDL ("good" cholesterol) to go up, and triglycerides to drop on a low-carb diet. LDL ("bad" cholesterol) is more variable in it's response. More about lipids on a low-carb diet:

Symptoms to Track

It's a very good idea to keep track of symptoms you may have that often respond to a reduction in carbohydrate.

You might just write a few paragraphs about your symptoms before starting your diet so that you will remember. It's very common for memory to fade about things like this. Also, any gastro-intestinal symptoms are good to make note of. More than one person has serendipitously found out about food allergies or sensitivities when changing their diet.

Things to pay attention to include energy level, mood, ability to concentrate, heartburn and other GI symptoms, allergy symptoms, compulsive eating, joint or muscle pain, PMS symptoms, acne and other skin problems, and headaches.

I wish you all the best on your low-carb journey! Sign up for my newsletter, and find out the latest things I'm writing to help you along the way, along with recipes, food ideas, the latest science, and lots of tips.


Chan DC, Watts GF, Barrett PH, Burk V. Waist Circumference, waist-to-hip ratio and body mass index as predictors of adipose tissue compartments in men. QJM. 2003 Jun;96(6):441-7.

Ebbeling, Cara, Leidig, Michael, Feldman, Henry, et al. "Effects of a Low–Glycemic Load vs Low-Fat Diet in Obese Young Adults." Journal of the American Medical Association. 297.19 (2007):2092-2102.

Krauss, Ronald, et al. “Carbohydrate, Weight Loss, and Atherogenic Dyslipidemia.” American Journal of Clinical Nutrition 2006 May;83(5):1025-31.

Obesity Education Initiative, National Institutes of Health, et al, "Clinical Guidelines on the Evaluation, and Treatment of Overweight and Obesity in Adults"." Sept 1998.

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