In the initial stage of a low-carb diet, it's common to experience a few unpleasant physical side effects, such as nausea, fatigue and headaches. Don't rush to abandon your weight-loss plan because of the discomfort; your headaches will probably go away in a few days. If they persist, however, you may need to make some adjustments to your diet. And if you're in serious or persistent pain, consult a doctor to rule out any hidden medical reason.
During the "induction" period of your low-carb diet – that is, the first two weeks – your body has to adjust to a new regimen, one that is likely very different from your previous one. You may have had a carb-heavy diet in which you ate as many as 300 grams of carbs a day, which is within the current recommendations on a 2,000-calorie diet. But in the first stage of a low-carb diet, you may be limited to as few as 20 grams of "net" carbs a day -- the grams left after you subtract fiber from the total carbs in a food.
This radical dietary change can wreak havoc with your system until your body becomes accustomed to burning fat for fuel instead of carbs. It's common to come down with a bad case of the "induction flu," with headaches being one of the symptoms. Your headaches could have several causes, but they usually disappear on their own within three or four days of starting your diet, says Authority Nutrition. Some people take several weeks to adjust completely to the new diet, however, and you may just want to wait it out.
When you start a low-carb diet, the weight you drop is a loss of water, not fat. Because you're taking in so few carbs, your body has less glucose to process and needs less insulin – the hormone that transports glucose through your bloodstream. Insulin also makes your body retain sodium, so less insulin means your body excretes more of this mineral – a situation that can lead to an imbalance of electrolytes in your body and result in headaches.
Make sure you're drinking enough water throughout your low-carb diet. You might also try an unsweetened sports drink with electrolytes in the induction phase. Dr. Andreas Eenfeldt of DietDoctor.com suggests a DIY drink: Mix half a teaspoon of salt into a glass of water and take once daily. Alternately, drink some beef, chicken or bone broth, which will give you protein, too. If you have a history of high blood pressure, however, it's best to talk to your doctor before increasing your intake of dietary sodium.
Your headaches might also signify classic "withdrawal" symptoms. Say your diet has been heavy in sugary sodas, refined flour and other carbs. Then you go cold turkey during the induction period of a low-carb diet, adhering to the strict carb limits. Restriction of these carb-heavy foods may result in symptoms such as headaches, anxiety, shaking and disorientation, reports Food Addiction Research Education – similar to withdrawal from addictive substances. There is some scientific basis to the theory that "hyperpalatable foods" like sugar share a craving-and-reward effect with drugs like cocaine, according to a review published in 2013 in Current Opinion in Clinical Nutrition and Metabolic Care.
Easing Into a High-Protein, Low-Carb Diet
It can be hard to perform well at work or school when you're experiencing headaches and other flulike symptoms. If your schedule permits, try starting a low-carb diet when you have downtime, like at the start of a weekend or staycation, or during a break between school terms.
Another option is to individualize your dietary plans. Maybe 20 grams of net carbs a day is too few for your system to function well, and you would do better on 40 or 50 grams. Even Atkins, whose classic plan is very strict, offers an alternate, less limiting plan that starts at 40 grams of net carbs a day and advances from there.
Remember, one diet doesn't necessarily fit all, even if it's popular, and a completely different diet might work better for you. Ask your doctor or dietitian what sort of weight-loss plan might sync with your circumstances and needs.
- National Academies of Science: Dietary Reference Intakes: Macronutrients
- American Journal of Clinical Nutrition: Low-Carbohydrate Nutrition and Metabolism
- Authority Nutrition: 5 Most Common Low-Carb Mistakes
- Diet Doctor: Induction Flu
- FARE: What Is Withdrawal?
- Current Opinion in Clinical Nutrition and Metabolic Care: Sugar Addiction
- Atkins: Atkins 40 Overview
- Columbia University Go Ask Alice: Are Low-Carb Diets Safe?