Plain Language Summary
By reading this article, you will:
- Learn how the ketogenic diet affects your hunger
- Find out whether keto is better than other diets for appetite suppression
- Get insight into how protein, ketones, and other factors affect hunger
What we did, and why
Hunger is very important because it affects how much you eat. People typically feel hungrier after going on a diet. This is because the body wants to regain lost weight. If you could control hunger, then maybe weight loss could be easier and you might prevent weight regain.
We have combed through the ketogenic literature. Our goal was to find studies with data on appetite, hunger, satiety, and cravings.
After analyzing the data, we answered the following questions: "Will I be hungry on keto?" and "Do I need to count calories?", and "Is the ketogenic diet superior compared to other diets for controlling hunger?"
People eat fewer calories on keto
When following a ketogenic diet, people spontaneously eat fewer calories.
In ketogenic studies, subjects only had to restrict carbohydrates, and did not need to count calories. On average, they ate about 600 kcal less than their regular diet:
Figure by Sci-Fit.
People feel less hungry on keto
When you go on a weight loss diet, you typically feel hungrier. Surprisingly, the ketogenic diet does not seem to follow this trend. In most studies, people felt less hungry on keto.
Is the ketogenic diet better than other diets for hunger control?
With the data currently available, the ketogenic diet seems superior for reducing hunger.
Figure by Sci-Fit.
5 studies found that keto was superior to an alternative diet. 3 studies found no difference between groups. We discuss it in greater detail here.
Why is keto effective at reducing hunger and calories?
We could not identify a single reason, so here is a list of several:
- Protein is the most satiating macronutrient. People on the ketogenic diet typically eat more protein than they normally do.
- Ketones could reduce hunger. However, the data on this is still in its infancy.
- Liquid calories are calorie dense and not very satiating. You can hardly drink sodas and juices on keto, so you get to avoid liquid calories. The food you eat will be more satiating and filling.
- The diet is simple. Several research teams speculate that the simplicity of the diet helps reduce hunger and caloric intake.
- Very low energy diets can reduce hunger and increase satiety. They are typically less than 800 kcal per day, and are almost always ketogenic.
- You do not need to count calories. It might be easier to eat until you’re full instead of having to think about calories. Most of the ketogenic studies were ad libitum, meaning that people ate as much as they wanted. Obviously, they had to restrict foods rich in carbs to be in ketosis.
Does the ketogenic diet suppress appetite?
People spontaneously eat fewer calories on keto
People tend to eat fewer calories while on the ketogenic diet (Gibson et al., 2015; Aragon et al., 2017). This happens spontaneously, because they aren’t asked to restrict calories. Hence, this diet could fit you well if you dislike calorie counting.
“The efficacy of [Ketogenic Diets] is (...) often attributed to a suppression of appetite resulting in spontaneous decrease in energy intake”.
In the graph below you can see how many calories subjects consumed. Across 11 studies, subjects ate, on average, 2,331 ± 473 kcal at baseline, and 1,694 ± 390 kcal on the ketogenic diet.
Remember, these are ad-libitum studies! The subjects were not asked to restrict calories (only carbs).
Figure by Sci-Fit. We pooled the average caloric intake of the ketogenic studies in our analysis, and calculated the standard deviations. Data is extracted from 11 ad libitum ketogenic studies.
That is the good news.
The bad news is that people eat more calories and carbs after a while on the diet. In other words, adherence to the diet drops. This happens across all types of diets and isn’t unique to keto. We will cover adherence in the next part of our keto series!
Does keto make you eat fewer calories than other diets?
Sadly, most studies compare carb restricted keto groups to calorie restricted control groups. We can’t compare them directly.
Still, we have some relevant studies:
| Study | Caloric intake | Time of measurement | Calorie restriction? |
| Johnstone et al., 2008
Crossover |
Keto
~1732 kcal Moderate carb diet ~1899 kcal |
Week 4 | No |
| McAuley et al., 2005
RCT |
Atkins (keto)
−~500 kcal Zone −~500 kcal |
Week 8 | No |
| Dansinger et al., 2005
RCT |
Atkins
−193 kcal Ornish diet (low fat vegetarian) −554 kcal |
Week 4 | No |
| Gardner et al., 2007
RCT |
Atkins
−507 kcal Ornish diet −442 kcal |
Week 8 | No |
Non-ketogenic studies:
| Study | Caloric intake | Time of measurement | Calorie restriction? |
| Gardner et al., 2018 | Low fat
−633 kcal Low carb −642 kcal |
Week 12 | No |
| Weigle et al., 2005 | High protein
−441 kcal |
Week 12 | No |
Overall, the data on this specific question isn’t settled yet. We might do a full analysis in the future.
People feel less hungry on keto
Hunger is often increased when dieting (MacLean et al., 2011; Gibson et al., 2015). Yet, that may not be the case for the ketogenic diet (Gibson et al., 2015). In almost all of the studies we analyzed, the ketogenic diet lead to a decrease in hunger.
This is quite unexpected, and very promising.
In a few studies (seen below), the scientists reported how hunger changed over time. For example, in Nymo et al, hunger increased at day 3 but slowly dropped thereafter. Yet, subjects in the other three studies dropped down and stayed at low hunger levels.
Figure by Sci-Fit. Each bar represents a point at which hunger was measured. All four studies used the Visual Analogue Scale for rating hunger. Read more about how scientists measure hunger (internal link).
A high protein diet makes you satiated
A large body of evidence demonstrates that protein is the most satiating macronutrient.
Why does this matter? Because the ketogenic diet is typically moderate or high in protein. This could be one explanation for why people eat fewer calories and feel less hungry on keto.
The average american diet is typically low to moderate in protein. It is difficult to quantify exactly what “low protein” means, because it is somewhat arbitrary. With that said, anything below 1 g protein per kg bodyweight can be considered low. Especially if your goal is to maintain or increase muscle mass.
Yet, it’s hard to say whether it’s ketosis or the high protein that causes people to eat fewer calories. For example, in Weigle et al., 2005 people ate −441 kcal per day when put on a high protein, normal carb diet. In McAuley et al., 2005, both the Zone group and the Atkins (keto) group ate ~−500 kcal after 8 weeks. This might be because both groups were high in protein. So in studies where the keto group ate more protein than the control diet, we would expect greater satiety for keto.
Exceptions to the rule:
“[the ketogenic diet] has demonstrated hunger-suppressive effects independent of protein content.”
- Protein intake wasn’t “high” in Nickols-Richardson et al., 2005 (94 g or 1.2 g/kg for keto), or in Foster et al., 1992 (70–90 g or ~0.7–0.9 g/kg). They still had a large decrease in hunger.
- In Saslow et al., 2014, the control group ate ~68 g or 0.7 g/kg protein and had the same reduction in hunger as the keto group (~106 g or 1.12 g/kg protein).
- Protein was moderate in Johnstone et al., 2008 (123g or 1.2 g/kg for keto vs 135 g or 1.3 g/kg for control). If protein is the main reason for appetite suppression, why didn’t the control group reduce their hunger to the same extent as keto?
- In studies where subjects eat Very Low Energy Diets (VLEDs), keto groups increase satiety and decrease hunger on 500-800 kcal and 50-60 g protein per day (i.e. Kovacs et al., 2004). If protein is so important, how come people feel so satiated on these types of diets (Gibson et al., 2015)?
These examples suggest that many factors affect satiety, beyond protein. We’ve covered some of the factors further down. [link to section].
Read more: a high protein diet does not prevent ketosis.
Ketone bodies might suppress your appetite
Several studies mention that ketone bodies could suppress appetite (Jabbek et al., 2010; Veldhorst et al., 2012; Pesta and Samuel, 2014; Gibson et al., 2015; Karl et al., 2016). It is possible that ketone bodies accomplish this by altering hunger hormones (Sumithran et al., 2013; Stubbs et al, 2017). For example, Sumithran et al., 2013 reported correlations between hunger hormones and ketones.
Although, this doesn’t explain why subjects on moderate and high carb diets feel less hungry. This suggests that ketones might play a role in appetite suppression, but they’re not the sole reason. Researchers generally agree that this is a hypothesis (Brehm et al. 2005; Gibson et al., 2015).
There are some interesting studies out there, such as Stubbs et al., 2017. The subjects were given a ketone drink which reduced their hunger and desire to eat over 4 hours. Yet, we need to see more long-term data on this topic.
“The increased concentration of beta-hydroxybutyrate may act as an appetite suppressing substrate [62].” - Pesta and Samuel, 2014
Correlating carbs and hunger
We graphed hunger and carb intake to see if they correlate. In our analysis we excluded studies with more than 80 g of carbohydrates. We found a moderate linear correlation (Pearson’s R = 0.54) between hunger change and carb intake. If we assume that there is a connection between ketosis and hunger, then carbs might influence hunger on a ketogenic diet.
Figure by Sci-Fit. Note that we should interpret the correlation carefully. By itself, it does not suggest that fewer carbs = less hunger.
Keto might affect cravings
Below, you see a graph of cravings. Every sphere represents a ketogenic diet group. The size of the sphere reflects how many subjects were in the study. For instance, the Foster et al., 1992 study had over 200 participants, so the sphere is much larger than the Rosen et al., 1982 study which had 8 participants.
There is a lot of variability in how keto affects cravings. There is data to suggest (not pictured) that those on a keto diet (Martin et al., 2011) have lower cravings for carbs or sweets compared to people on a low-fat diet.
Note that a craving is different from hunger. You can crave a specific food while feeling satiated, in general.
Figure by Sci-Fit. The cravings were measured using a 5-point scale. A drop in cravings by ~33% (as seen in Saslow et al., 2014) is notable, because they went from rarely feeling carb cravings to almost never feeling a craving. It’s hard to say what the practical implications of this is in the long-term
How scientists measure appetite
Appetite is hard to measure objectively. After all, how hungry or full you feel is subjective. However, scientists have developed several tools to measure satiety, hunger, appetite, and cravings.
Visual Analogue Scale (subjective)
The Visual Analogue Scale uses a line that is 100 mm in length. Zero on the line represents “not hungry” and 100 represents “extremely hungry”. This tool can be used for hunger, appetite, satiety, cravings, etc. Study participants are asked to make a mark on the line corresponding to how hungry they feel. You can see an example of the scale below:
Visual analogue scale ratings for hunger, desire to eat, and appetite can be related to subsequent food intake (Flint et al., 1998).
Appetite hormones (objective)
We can measure appetite objectively by looking at hormones. Hormones are measured in blood and can help explain why our appetite changes during or after a diet.
Below is a table of hormones and their effects on appetite:
Table by Sci-Fit, adapted from Pliquett et al., 2006
For more information on what these hormones do,
Three Factor Eating Questionnaire (subjective)
Aside from the visual analog scale, the nutrition field has other methods to quantify food cravings and hunger. One of those is the Three Factor Eating Questionnaire. It measures three dimensions of eating: disinhibition, hunger, and cognitive restraint (Stunkard and Messick, 1985).
Food Craving Inventory (subjective)
The Food Craving Inventory is a self-reported measure of specific food cravings (White et al., 2002).
Subjects rate how frequently they feel cravings to eat certain types of foods:
- Carbohydrate-cravings
- Fast-food cravings
- Sweet cravings
- Fat cravings
They use a 5-point scale:
- Never feel a craving
- Rarely feel a craving
- Sometimes feel a craving
- Often feel a craving
- Daily/continual cravings