Low carbohydrate also known as ketogenic diets gained popularity across the globe and many fitness influencers, as well as elite athletes, gave it a try. In the team of ”keto lovers”, it is highly praised as THE diet where you magically lose weight, and your body is transformed into the fat-burning machine. Sure. The body can’t burn carbohydrates if there aren’t any around. It is also true that a ketogenic diet is an effective way to treat certain medical conditions. But this is not what this article is about. The intention is to take a look at the consequences a low carbohydrate diet has on the hormones and health in female athletes.
Region of our brain called hypothalamus regulates energy balance by regulating the nutrient levels in storage organs (fat in adipose tissue, glycogen in the liver) and our food intake. It is continuously receiving information about energy stores, ingested food, the composition of the food and energy demand by the tissues. For example, leptin and insulin are two of those hormones, that are secreted in the proportion to the amount of fat, glycogen and overall energy availability in the body. The brain responds by secreting hormones and factors, which influence your energy intake, food choices and energy expenditure.
At this point, we have to clarify that this is just how well the regulation is working in healthy subjects. For example, if one would eat just 100kcal extra every day, one would gain 5 kg in one year. If a bodyweight of an individual drops due to caloric deficit, insulin and leptin secretions drop as a consequence. Brain primes the body for the intake of larger meals and larger meals need to be ingested for the achievement of sufficient satiation signal to stop eating.
Keto diet changes endocrine response in the brain
In the keto diet, most of the energy is consumed with fat. Lack of ingested carbohydrates and thus lack of insulin response influences signalling in the brain. It senses the absence of insulin and leptin and the presence of lipids and the absence of glucose in the blood. As the blood glucose is low, body goes into a starvation state called nutritional ketosis. Nutritional ketosis is a metabolic state of elevated blood ketone bodies, as a result of low glucose. Lack of insulin and glucose signal is sensed by the hypothalamus which results in a lower LH pulsatility. The pituitary gland releases the LH hormone, which signals to the ovaries. Lower pulses of LH and less frequent pulses do not stimulate the ovaries enough to produce a sufficient amount of oestrogen and consequently, there are lower oestrogen levels, at least in women. The second part of the story belongs to the cortisol. Ketogenic diet has been linked to an increased levels of circulating cortisol. Cortisol also signals to the pituitary gland, that additionally decreases the secretion of LH and thus decreases the production of sex hormones.
Keto diet and the bones
Reduced bone mineral density is one of the key outcomes of REDs. Females with menstrual dysfunction (low oestrogen levels) have deteriorated bone microarchitecture and reduced bone formation. Similar is observed in males with testosterone deficiency. Athletes with RED S experience stress fractures more often compared to the healthy counterparts. A very recent study (Heikura et al, 2020) on the effect of the ketogenic diet found out that markers of bone formation were decreased, whereas markers of bone degradation were increased. Changes occurred in a short period of 3-3.5 weeks upon the intervention.