Ketogenic diets can reduce the increase in hunger otherwise seen with diet-induced weight loss.However, it’s not clear whether carb intake needs to be severely low (<50 g/day) to achieve ketosis. A recent study examined three different carb intakes and their impacts on ketosis and appetite.
Overview
- What did they test? The authors conducted an eight week randomized controlled trial that compared three low-energy diets (1000 kcal/day) with different amounts of carbohydrate (low: 70g/day, medium: 100g/day or high: 130g/day) on ketosis and changes in hunger feelings in adults with obesity.
- What did they find? All groups achieved ketosis during the eight-week study, irrespective of carbohydrate quantity. The study found no significant differences in hunger across the three diets.
- What does it mean for you? Obese adults looking to lose weight may wish to follow low energy diets with up to 130g/day of carbohydrate to induce ketosis and weight loss, while reducing potential increase in hunger from dieting. However, more research is needed to confirm this finding.
What’s the problem?
Purpose
Diet-induced weight loss often comes with an unwelcome side effect: increased hunger. This hunger surge, driven by elevated ghrelin levels, can make it harder to stick to weight loss ‘diets’, contributing to high dropout rates 1. Therefore, finding effective strategies to curb appetite while achieving significant fat loss, could improve both long term compliance and weight loss outcomes.
One diet that has received much attention is the ketogenic diet due to its ability to suppress appetite. When individuals are in ketosis, they consistently report feeling less hungry 2 and, at times, fuller after a meal compared with the non-ketotic state. This appetite suppression is thought to stem from hormonal adaptations, particularly the prevention of ghrelin increases typically associated with weight loss 3. These effects suggest that ketogenic diets may enhance adherence to weight loss programs by lowering appetite 2.
However, traditional ketogenic diets require restricting carbohydrate intake to less than 50g per day which does not align with nutritional guidelines, and often excludes nutrient-dense food groups like whole grains, fruits, and vegetables 4. This is of concern because it might lead to nutritional inadequacy, increased risk of constipation, and diseases in the long term such as certain types of cancer, osteoporosis, and cardiovascular disease 5.
Existing literature has suggested that ketosis can be achieved at carbohydrate intakes greater than 50 g but less than 100g per day 2, raising the question as to how much carbohydrate restriction is needed to induce ketosis and suppress appetite. The ability to maximize carbohydrate intake while preventing the increase in hunger would allow individuals seeking weight loss to increase their intake, in particular nutrient dense carbohydrates, and perhaps improve adherence to weight loss programmes.
Therefore, in this article, we will look at a randomized controlled trial (RCT) that compared three low-energy diets (LEDs) with different amounts of carbohydrate on ketosis and changes in hunger feelings in adults with obesity.
Hypothesis
The authors hypothesized that weight loss induced by isocaloric LEDs with varying carbohydrate levels would not significantly affect hunger feelings. Additionally, they suggested ketosis could occur at carbohydrate intakes above 100 g/day without significantly increasing hunger.
What Did They Test and How?
Participants
A total of 101 healthy, weight-stable (<2kg variation in body weight within the last three months), adult (ages 18–65 years) men and women with obesity (body mass index (BMI) 30–45 kg/m2) who were not actively trying to lose weight (self-reported) were recruited through advertisements in Trondheim, Norway, from May 2017 to August 2018. See Figure 1 for the study flow diagram.
Study participants included women who were either postmenopausal, taking oral contraceptives, or had a normal menstrual cycle (i.e., mean duration 28 days). Measurements were taken in the same phase of the menstrual cycle as this has been shown to modulate appetite 6. Participants who were pregnant or breastfeeding, had a history of drug or alcohol abuse, were taking medication known to affect appetite or induce weight loss, had a history of psychological or eating disorders, had lactose intolerance, or had had bariatric surgery were ineligible to participate.
Figure 1: The ASKED trial flow diagram
