Low-calorie diets leading to rapid weight loss can cause headaches -- especially if your carbohydrate intake is too low. A study published in 2011 in the "Nutrition Journal" reports that symptoms of ketosis, which occurs when there is a buildup of metabolic byproducts called ketones in the body after breaking down fat instead of carbs as fuel -- include headaches, bad breath, weakness and constipation. To reduce your chance of getting a headache during weight loss, eat at least 130 grams of carbohydrates -- which is the recommended dietary allowance, or RDA -- daily and avoid losing more than 2 pounds per week.


As ingested CHO is broken down by the stomach and absorbed through the small intestine, rising blood sugar creates a feedback loop which results in secretion of insulin. The primary role of insulin is to “dispose” of excess blood sugar by signaling tissues to “uptake” more glucose from the circulating supply. In this manner insulin serves a prominent role in glucose regulation. This concept also provides the basis for the glycemic index, a concept which attempts to quantify the impact CHO foods have on blood sugar response. For example, foods rich in simple CHO (i.e., “sugars”), which are absorbed quickly, trigger a rapid rise in blood sugar (and subsequently insulin response), whereas foods rich in complex CHO, such as fiber-rich legumes, exert a relatively blunted response on blood glucose.
Because it lacks carbohydrates, a ketogenic diet is rich in proteins and fats. It typically includes plenty of meats, eggs, processed meats, sausages, cheeses, fish, nuts, butter, oils, seeds, and fibrous vegetables. Because it is so restrictive, it is really hard to follow over the long run. Carbohydrates normally account for at least 50% of the typical American diet. One of the main criticisms of this diet is that many people tend to eat too much protein and poor-quality fats from processed foods, with very few fruits and vegetables. Patients with kidney disease need to be cautious because this diet could worsen their condition. Additionally, some patients may feel a little tired in the beginning, while some may have bad breath, nausea, vomiting, constipation, and sleep problems.

However, maintaining muscle mass and its functionality (i.e., muscle strength) has an important role in preventing weight regain, maintaining physical functionality, improving cardiometabolic risk factors, and reducing cardiovascular outcomes (5, 7–9, 32, 33). It is commonly assumed, and stated in several textbooks on obesity, that weight loss is associated with an important loss of muscle mass that evolves in parallel with the fat reduction. Some dietary guidelines have even suggested that diets that induce rapid weight loss, such as VLCK diets, create a greater energy deficit and contain lower amounts of protein, and therefore increase the risk of reductions in muscle mass compared with other interventions with more gradual weight loss (34, 35). In this article it was shown that the reductions observed in lean mass were mostly a result of body water loss, both intra- and extracellular. The combined information from the DXA and MF-BIA methods allows for such differentiation (28, 36–38). The loss attributable to muscle mass was minimal (∼1 kg), and an absolute preservation of HG strength was observed, a remarkable fact considering that the patients have experienced a weight reduction of ∼20 kg.
At its core, weight loss results from burning more calories than you consume. But the macronutrient composition of those calories is also vital. Different foods have substantially different metabolic and hormonal effects on the body. So what’s eaten (and how calories are expended) can change how much you eat and whether those calories are burned or stored.
Over the past century, ketogenic diets have also been used as natural remedies to treat and even help reverse neurological disorders and cognitive impairments, including epilepsy, Alzheimer’s symptoms, manic depression and anxiety. Research shows that cutting off glucose levels with a very low-carb diet makes your body produce ketones for fuel. This change can help to reverse neurological disorders and cognitive impairment, including inducing seizure control. The brain is able to use this alternative source of energy instead of the cellular energy pathways that aren’t functioning normally in patients with brain disorders.
4. Gomez-Arbelaez D., Bellido D., Castro A.I., Ordonez-Mayan L., Carreira J., Galban C., Martinez-Olmos M.A., Crujeiras A.B., Sajoux I., Casanueva F.F. Body composition changes after very-low-calorie ketogenic diet in obesity evaluated by 3 standardized methods. J. Clin. Endocrinol. Metab. 2017;102:488–498. doi: 10.1210/jc.2016-2385. [PubMed] [CrossRef] [Google Scholar]
“I discovered the low-carb, ketogenic diet some four years ago and saw huge improvements in my own health. After establishing that it is based on sound scientific principles I felt compelled to offer it to my patients. We recommend the Diet Doctor website as it offers an unbiased, contemporary source of reliable low-carb ketogenic advice. It is easy to use and you can rely on its integrity.”
Previous studies have shown that ketogenic diets preferably reduce the total FM in obese patients (10–13). However, the precise distribution of these losses has not been determined. In this study we confirmed that the diet reduces total FM and specifically visceral adipose tissue, which has a greater impact in predicting cardiometabolic complications associated with obesity than does the total volume of body adiposity (2, 31). 

Basically, carbohydrates are the primary source of energy production in body tissues. When the body is deprived of carbohydrates due to reducing intake to less than 50g per day, insulin secretion is significantly reduced and the body enters a catabolic state. Glycogen stores deplete, forcing the body to go through certain metabolic changes. Two metabolic processes come into action when there is low carbohydrate availability in body tissues: gluconeogenesis and ketogenesis.[4][5]
In regard to serum measurements, the mean fasting glucose decreased by 17% from 9.08 ± 4.09 mmol/L at baseline to 7.57 ± 2.63 mmol/L at week 16 (p = 0.04) (Table ​(Table4).4). Serum sodium and chloride levels increased significantly, but only by 1% and 3%, respectively. Uric acid level decreased by 10% (p = 0.01). Serum triglyceride decreased 42% from 2.69 ± 2.87 mmol/L to 1.57 ± 1.38 mmol/L (p = 0.001). Increases occurred in both high-density lipoprotein (HDL) cholesterol (8%) and low-density lipoprotein (LDL) cholesterol (10%) but these changes were of borderline statistical significance (p = 0.08 and p = 0.1, respectively). The following blood tests did not change significantly: total cholesterol, potassium, bicarbonate, urea nitrogen, creatinine, calcium, thyroid-stimulating hormone, and hemoglobin.

In steps 4 or 5, the ketogenic phases were ended by the physician in charge of the patient based on the amount of weight lost, and the patient started a low-calorie diet (800–1500 kcal/day). At this point, the patients underwent a progressive incorporation of different food groups and participated in a program of alimentary re-education to guarantee the long-term maintenance of the weight loss. The maintenance diet consisted of an eating plan balanced in carbohydrates, protein, and fat. Depending on the individual, the calories consumed ranged between 1500 and 2000 kcal/day, and the target was to maintain the weight lost and promote a healthy lifestyle.

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