Are you struggling while starting out on a low-carb or keto diet? Do you get headaches, leg cramps, constipation or any of the other more common side effects? Use the information on this page to avoid them – and feel great while losing weight.
The main solution to most common problems when starting low carb is to increase the intake of water and salt. It’s even better to do it preventatively during the first week. If you do, you’ll most likely not experience any of these problems, or they’ll only be minor.
Use one of the shortcuts below for specific problems – or just continue reading for all of them.
- 1 Induction flu: Headaches, lethargy, nausea, confusion, brain fog, irritability
- 2 The cure: water & salt
- 3 The bonus: more fat
- 4 If necessary
- 5 Learn more
- 6 Leg cramps
- 7 Six ways to kick nasty leg cramps to the curb
- 8 Constipation
- 9 Bad breath
- 10 Heart palpitations
- 11 The cure
- 12 If necessary
- 13 Important note if on medication for diabetes or high blood pressure
- 14 Diabetes
- 15 High blood pressure
- 16 Reduced physical performance
- 17 Increasing physical performance on low carb
Induction flu: Headaches, lethargy, nausea, confusion, brain fog, irritability
The most common side effect on low carb is what most people experience during the first week, often on day 2-4. The “induction flu”, so called as it can mimic flu-like symptoms.
Headaches are very common during this transition, as is feeling tired, lethargic and unmotivated. Nausea is also common. It’s also possible to experience confusion or “brain fog” – feeling not smart at all. Finally, it’s common to feel irritable – perhaps most clearly experienced by the rest of your family.
The good news is that these symptoms usually disappear by themselves within a few days. The even-better news is that these symptoms can often be avoided altogether. The main cause is usually dehydration and/or salt deficiency, caused by a temporarily increased urine production.
The cure: water & salt
Any problems can be minimized, and sometimes entirely cured, by getting enough water and salt into your system.
For example try adding half a teaspoon of salt to a large glass of water. Drink it. This may reduce or eliminate side effects within 15-30 minutes. If so, this may be repeated once daily if needed during the first week.
A better-tasting option is to use broth or bouillon, e.g. chicken, beef or bone broth.
The bonus: more fat
Make sure to eat enough fat. Going low carb, low fat is a recipe for starvation and feeling hungry and tired. You should never endure hunger as you start on a low-carb diet. A proper low-carb diet contains enough fat to make you feel satiated and energetic. This can speed up the transition time and minimize the time spent feeling low when starting low carb.
So how do you get enough fat on low carb? There are any number of options, but when in doubt add butter to whatever you’re eating.
If adding salt and water (and fat) does not completely eliminate the induction flu the best option is usually to just hang in there. Any remaining symptoms are likely to be resolved within days, as your body adapts to low carb and turns into a fat-burning machine.
If necessary, it’s of course possible to have some carbs and make the transition to low carb more gradual and slower. This is not recommended as a first option, as it slows down the process and makes the weight loss and health improvement less obvious immediately.
Learn morefree trial one month).
Avoiding transition problems like the induction flu is covered in part 3/5
Leg cramps are not uncommon when starting a strict low-carb diet. It’s usually a minor issue if it occurs, but it can sometimes be painful. It’s a side effect of the loss of minerals, specifically magnesium, due to increased urination. Here’s how to avoid it:
- Drink plenty of fluid and get enough salt.This may reduce loss of magnesium and help prevent leg cramps.
- If needed, supplement with magnesium.Here’s a suggested dosage from the book The Art and Science of Low Carbohydrate Living by Drs. Jeff Volek and Stephen Phinney: Take 3 slow-release magnesium tablets like Slow-Magor Mag 64 a day for 20 days, then continue taking 1 tablet a day afterwards.
- If the steps above are not enough and the problem is bothersome, consider increasing your carb intake somewhat. This should eliminate the problem. The more carbs you eat though, the weaker the impact of the low-carb diet.
Alternatively, for even more information and tips, check out our full guide:
Six ways to kick nasty leg cramps to the curb
GUIDE Here are the six key things to know to kick your leg cramps to the curb, in our full leg cramps guide.
Constipation is another possible side effect, especially during the first time on a low-carb diet, as your digestive system may need time to adapt.
Here are the three steps to cure it, perhaps you only need the first one:
- Drink plenty of fluid and get enough salt.The most common cause of constipation on low carb is dehydration. This makes the body absorb more water from the colon and thus the contents get dryer, harder and constipation can result. The solution is to drink plenty of water and perhaps add some extra salt.
- Eat plenty of vegetables or another source of fiber. Getting enough good quality fiber from the diet keeps the intestines moving and reduces the risk of constipation. This can be more of a challenge on low carb where many sources of fiber are avoided, but eating plenty of non-starchy vegetables may solve this problem. Another, and completely carb-free, option for adding fiber to the diet is psyllium seed husks (can be dissolved in water).
- If the steps above are not enough, use Milk of Magnesia to relieve constipation. Amazon link
On a strict low-carb diet some people experience a characteristic smell from their breath, a fruity smell that often remind people of nail polish remover.
The smell is from acetone, a ketone body. This is a sign that your body is burning lots of fat and even converting lots of fat to ketones to fuel the brain. You are a fat-burning machine.
This smell can sometimes also turn up as body odor, especially if working out and sweating a lot.
Not everyone eating a ketogenic low-carb diet ever experience this ketone breath – and for most people who do it’s a temporary thing that goes away after a week or two. The body then adapts and stops “leaking” ketones through breath and sweat.
For some people it does not go away though, and it can be a problem. Here are the possible solutions. The first two are more general, the next three more targeted to the keto smell specifically.
- Drink enough fluid and get enough salt. If your mouth feels dry – and it often can when just starting a strict low-carb diet and getting into ketosis – this means you have less saliva to wash away bacteria. This can result in bad breath, so make sure to drink enough.
- Maintain a good oral hygiene. Brushing your teeth twice a day won’t stop the fruity keto smell (that comes from your lungs), but at least it won’t be mixing with other smells.
- Use a breath freshener regularly. This can mask the keto smell.
- Wait another week or two and hope for it to be temporary (most often it is).
- Reduce the degree of ketosis. If the smell is a long-term problem and you want to get rid of it, the easy way is to reduce the degree of ketosis. This means eating a bit more carbs, 50-70 grams per day is usually enough to get out of ketosis. Of course, this will reduce the effect of the low-carb diet when it comes to weight loss and diabetes etc., but for some people it can still be powerful enough. Another option is to eat 50-70 grams of carbs per day and add some intermittent fasting. This can get you roughly the same effect as a strict low-carb diet… without the smell.
It’s common to experience a slightly elevated heart rate during the first few weeks on low carb. It’s also common to experience that the heart is beating a bit harder. This is normal and usually nothing to worry about.
One common cause is dehydration and a lack of salt. A reduction in the amount of circulating fluid in the blood stream means that the heart will have to pump blood slightly harder or faster to maintain blood pressure.
The quick solution to this problem is to drink enough fluids and make sure to get enough salt.
If adding salt and water does not completely eliminate heart palpitations, it can also be a result of stress hormones released to maintain blood sugar levels (if you’re on diabetes medication see section below). This is usually a temporary problem as the body adapts to a lower-carb diet. It should go away within a week or two.
In the uncommon situation that the problem persists – and the palpitations are bothersome to you – try to slightly increase the carb intake. This will reduce the effect of the low-carb diet somewhat, so it’s a trade-off.
Some people also recommend supplementing with magnesium to decrease palpitations.
Important note if on medication for diabetes or high blood pressure
Avoiding the carbohydrates that raise your blood sugar decreases your need for medication to lower it. Taking the same dose of insulin as you did prior to adopting a low-carb diet might result in a low blood sugar. One of the main symptoms of this is heart palpitations.
You need to monitor your blood sugar frequently when starting this diet and adapt (lower) your medication. This should ideally be done with the assistance of a knowledgeable physician. If you’re healthy or a diabetic treated either by diet alone or just with Metformin there is no risk of hypoglycemia.
High blood pressure
On a low-carb diet an elevated blood pressure tends to improve (normalize). This reduces the need for medication and your dosage may become too strong, leading to low blood pressure. One of the symptoms of this can be an increased pulse and heart palpitations. If you experience this it’s wise to check your blood pressure (here’s a good home monitor). If it’s low – e.g. under 110/70 – you should contact your doctor to discuss possibly reducing or discontinuing your blood pressure medication.
Reduced physical performance
In the first few weeks on a low-carb diet your physical performance can be severely reduced. There are two main reasons for this:
- Lack of fluid and salts. This cause of most early problems when starting low carb is a real killer when it comes to physical performance. Drinking a large glass of water with 0.5 teaspoons of salt 30–60 minutes before exercising is the solution, and can make a huge difference in performance.
- Adaptation to burning fat takes weeks.The second cause of reduced early performance is not as quickly fixed. It simply takes time for your body to shift from being a sugar-burner to burning primarily fat for energy, even in the muscles. It takes weeks or a few months. This adaptation will be faster the more you exercise while on a low carb, high fat diet. The end result has many benefits (see below).
Increasing physical performance on low carb
While transitioning to a low carb, high fat (LCHF) diet often reduces early physical performance, the long-term effect has many benefits. This is something that has only recently begun to be appreciated. In fact, a lot of elite athletes are now experimenting with LCHF diets and in some cases they are now crushing the competition.
The benefits of a LCHF diet in sports are mainly seen in long-distance running and other endurance events. The body’s fat stores are huge as opposed to the minuscule glycogen stores. This means that once fat-adapted, an athlete can perform for long periods of time without needing much (if any) external energy. This frees the athlete from having to activate his or her gastrointestinal organs during activity – a large amount of blood flow can instead be directed to the muscles. This also minimizes the risk of digestive issues during the activity.
Another benefit comes from the reduction of body fat usually seen on low carb. This reduction in body-fat percentage and lightening of your body is a huge bonus for most sports.