Weight loss, improved physical performance, cognitive function, eating behavior, and metabolic profile in a 12-week ketogenic diet in obese adults

Abstract

The ketogenic diet (KD) is being increasingly promoted as a strategy to fight obesity. Although the KD is effective for weight loss and weight control, comprehensive determination of its relationship with biochemical, physiological and psychological changes is still largely unexplored. We hypothesized that a 12-week KD (12KD) would significantly affect body weight, physical performance, cognitive function, eating behaviors, the metabolic and hormonal profile in obese adults, although differently in men and women. In an uncontrolled intervention, 35 sedentary obese adults (13 men, 25 women), aged 37 ± 7 years with a BMI 36.1 ± 5.6 kg/m² underwent a 12KD between March 2017 and June 2017 at the University of Primorska. The 12KD resulted in decreased appetite, significant weight loss of participants (−18 ± 9 kg men vs. -11 ± 3 kg women; P < .001), decreased emotional and external eating (P < .001 for both), increased body image satisfaction (P < .001) and improved physical performance (P < .001). Biochemically, a significant drop in glucose (P = .026), and a significant increase in LDL-cholesterol (P = .031), CRP (P = .007), and BDNF (P = .035) were observed in the first 2 weeks; then, all listed parameters returned to baseline. On the other hand, a significant reduction in insulin (P < .001) and leptin levels (P < .001), and a significant increase in adiponectin (P = .008) and NPY (P = .009) were detected throughout the duration of the 12KD. Our results show the efficacy of the 12KD on weight loss, physical performance, cognitive function, eating behaviors and metabolic profile. However, the long-term effects of a KD on these outcomes needs to be further studied before general recommendations can be made.

Introduction

The ketogenic diet (KD) is increasingly being promoted as a strategy to fight obesity in the general population through anecdotes, best-selling books, lay publications and social media. For clinicians to tackle the obesity epidemic, which is one of the greatest global public health challenges [1], the knowledge and clinical evaluation of the strategies used by patients, together with evidence-based treatments with health benefits for the whole organism, that are practical and feasible to implement, are of extreme importance to prevent miscommunications based on unscientific beliefs [2] on both sides-the patient and the physician. The KD as a possible tool to fight obesity is also gaining attention in medical circles and scientific literature [3].

Ketosis, which is thought to be a key factor in the efficacy of very low energy diets (VLED) [4], [5] and the KD, [6], [7], [8] is reported to suppress the drive to eat. The KD has undoubtedly been proven to be an effective tool to fight obesity in the short to medium term [9], [10], to improve glycemic control, and reduce some cardiovascular risk factors [11], [12], [13], [14]. In addition, Davidson and colleagues [15] suggested that ketones may protect against the cognitive impairment caused by weight gain and obesity. In fact, elevated levels of ketones exerted neuroprotective effects in the hippocampus [16], the specific brain region associated with cognitive performance, and they have been suggested to have therapeutic effects on some brain disorders such as mild cognitive dementia [17]. Moreover, a KD may also have positive effects on mood in overweight subjects [18]. The KD has been associated with reductions in the negative effects [19], and with significant alterations in levels of serotonin and dopamine neurotransmitters [20], which are both implicated in anxiety and depression. The exact mechanisms through which a KD can promote weight loss remains to be determined, and some concerns among physicians about safety are still present [21], [22]. Although a KD is effective for weight loss and weight control, a comprehensive determination of its relationship with fat and lean mass loss, metabolic states, physical and psychological function, and inflammatory and hormonal profiles is still largely unexplored.

Considering the reported positive effects of a KD, we hypothesized that a 12-week ketogenic diet (12KD) would cause the loss of body weight without significant negative effects on metabolic, physiological and psychological parameters. To test this hypothesis, this uncontrolled intervention study was designed to evaluate the effects of a KD on body composition, physical performance, cognitive function, eating behaviors, lipid and glucose profiles and a broad range of inflammatory and hormonal responses in obese adults following a 12 week intervention period. Moreover, the additional aim of this study was to examine the timeline over which changes in subjective and objective parameters of health status occur during the intervention and to detect potential differences between genders.