Can a Reduction in Carbohydrate Consumption Produce Adverse Effects?

Jorge Pincay ’20

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Figure 1. A sudden decrease in carbohydrate consumption can have negative effects on the human body.

Low carbohydrate  diets (LCD) have been adopted by many patients as a means of battling diseases such as cancer, diabetes, obesity, and many other metabolic disorders. This type of diet is even widely used by the general population for maintaining and/or losing weight. However, not many studies  have investigated the adverse health effects that may result from a sudden halt in carbohydrates intake. While little research has been done on this topic, some studies have found that symptoms occurring after carbohydrate withdrawal may include headaches, constipation, halitosis, muscle cramps, bloating, diarrhea, general weakness, and rash. 

Scientists from the AUT University in New Zealand   recently conducted a study to investigate the effects of carbohydrate withdrawal on a group of 77 people, comprised of 25 males and 52 females. The mean age was about 39 years old, and the mean body mass index (BMI) was 27 kg/m2. Study participants were assigned to one of three diets, each of which differed in the restricted amount of carbohydrates. Participants were asked to maintain their diet for a three week period. These three diets included the very-low carbohydrate ketogenic diet (VLCKD), the low-carbohydrate diet (LCD), and the moderately low-carbohydrate diet (MCD). The total energy (TE) derived from carbohydrates for each of these diets was 5%, 15%, and 25%, respectively. Fasting blood ketone concentrations were recorded daily upon waking for each individual to measure levels of beta-hydroxybutyrate (β-OHB), a ketone that serves as the preferred source of fuel for the body in conditions of depleted glucose levels . Additionally, individuals were asked to answer a sum of symptom score (SOSS) questionnaire that was based on a 5-point mood-scale.

Over the three weeks, results showed that serum levels of β-OHB rose for all three groups. The increases in the levels of β-OHB for participants in the MCD, the LCD, and the VLCKD groupwere 0.270.32, 0.410.38, and 0.620.49, respectively. The elevated plasma concentrations of β-OHB indicated that ketosis, a state in which the body burns fat for energy due to limited availability of carbohydrates, was achieved for all participants in the study, with the greater number of ketogenic individuals being found in the VLCKD group. Furthermore, the results of the SOSS showed a small, yet significant, increase in headache severity, constipation, diarrhea, halitosis (change in breath odor), muscle cramps, and muscle weakness across all groups. Halitosis and muscle weakness was found to be highest in the VLCKD group. 

Significant reduction in carbohydrates, as seen in the diets of this study, can have both beneficial and adverse effects. Perhaps one day, further studies in this field could lead to the development of drugs for the alleviation or complete removal of these symptoms. Ultimately, the combination of these drugs with LCDs may allow patients to benefit from these diets without experiencing the negative symptoms associated with carbohydrate withdrawal. 




  • Harvey et al., Effects of differing levels of carbohydrate restriction on the achievement of nutritional ketosis, mood, and symptoms of carbohydrate withdrawal in healthy adults: A randomized clinical trial, Nutrition X, 2019, 




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