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Sex differences exist from birth, yet are often under-reported in exercise and nutrition research. Often women are excluded or grouped with men, without menstrual cycle phase acknowledgement. The aim of this talk is to describe sex differences as they apply to performance parameters of thermoregulation, hydration/hyponatremia, and thirst. The perturbations of sex hormones across the menstrual cycle induce several metabolic, thermoregulatory, and neuroendocrine challenges, which may impact performance. Women, compared to men, have higher body surface area to body mass ratio, higher body fat mass, and higher density and number of sweat glands. Women also use a higher percentage of sweat glands while secreting less sweat. These facts may cause inherent differences in tolerance to heat between the sexes. Women are at greater risk for exercise-induced hyponatremia (low blood sodium concentration) and this risk has been attributed to their lower body weight and size, excess water ingestion, and estrogen-mediated inhibition of potassium transfer. Moreover, the greater levels of estradiol in plasma and tissue also play a role in increasing the risk of hyponatremia in women. The hormonal influences of sex hormones affect fluid dynamics by altering capillary permeability, vasomotor function, and the central set-point control of renal hormones and plasma osmolality. Elevations in plasma progesterone concentrations during the luteal phase inhibit aldosterone-dependent sodium reabsorption at the kidneys due to progesterone competing with aldosterone for the mineralocorticoid receptor. Moreover, progesterone is thermogenic, induce a core body temperature rise by 0.5'C; with concomitant resetting of cutaneous vasodilation and the osmotic set-point for thirst. [ABSTRACT FROM AUTHOR]

Position Statement: The International Society of Sports Nutrition (ISSN) provides an objective and critical review of the use of a ketogenic diet in healthy exercising adults, with a focus on exercise performance and body composition. However, this review does not address the use of exogenous ketone supplements. The following points summarize the position of the ISSN., 1. A ketogenic diet induces a state of nutritional ketosis, which is generally defined as serum ketone levels above 0.5 mM. While many factors can impact what amount of daily carbohydrate intake will result in these levels, a broad guideline is a daily dietary carbohydrate intake of less than 50 grams per day., 2. Nutritional ketosis achieved through carbohydrate restriction and a high dietary fat intake is not intrinsically harmful and should not be confused with ketoacidosis, a life-threatening condition most commonly seen in clinical populations and metabolic dysregulation., 3. A ketogenic diet has largely neutral or detrimental effects on athletic performance compared to a diet higher in carbohydrates and lower in fat, despite achieving significantly elevated levels of fat oxidation during exercise (~1.5 g/min)., 4. The endurance effects of a ketogenic diet may be influenced by both training status and duration of the dietary intervention, but further research is necessary to elucidate these possibilities. All studies involving elite athletes showed a performance decrement from a ketogenic diet, all lasting six weeks or less. Of the two studies lasting more than six weeks, only one reported a statistically significant benefit of a ketogenic diet., 5. A ketogenic diet tends to have similar effects on maximal strength or strength gains from a resistance training program compared to a diet higher in carbohydrates. However, a minority of studies show superior effects of non-ketogenic comparators., 6. When compared to a diet higher in carbohydrates and lower in fat, a ketogenic diet may cause greater losses in body weight, fat mass, and fat-free mass, but may also heighten losses of lean tissue. However, this is likely due to differences in calorie and protein intake, as well as shifts in fluid balance., 7. There is insufficient evidence to determine if a ketogenic diet affects males and females differently. However, there is a strong mechanistic basis for sex differences to exist in response to a ketogenic diet.