Is Low Carb a Bad Mood Diet?

Abstract & Commentary

By Joseph E. Scherger, MD, MPH, Clinical Professor, University of California, San Diego. Dr. Scherger reports no financial relationship to this field of study.

Synopsis: A very low-carbohydrate diet results in similar weight loss as a low-fat diet, but participants on a low-fat diet have improved psychological mood and well-being compared with those on a low-carbohydrate diet.

Source: Brinkworth GD, et al. Long-term effects of a very low- carbohydrate diet and a low-fat diet on mood and cognitive function. Arch Intern Med 2009;169:1873-1880.

A study group in Australia performed a randomized controlled trial of 106 overweight and obese participants on a very low-carbohydrate diet without fat restriction (similar to the Atkins Diet) and a more conventional low-fat diet without carbohydrate restriction. The two groups were followed for 1 year. The focus of the study was to look for changes in body weight, psychological mood, and cognitive function. Mood was assessed using the Profile of Mood States, the Beck Depression Inventory, and the Spielberger State Anxiety Inventory. Standard measurements were made for body weight and memory function.

The overall mean weight loss over 1 year was 13.7 kg with no significant difference between the groups (P = 0.26). All three measures of mood improved in the low-fat group compared with the low-carbohydrate group (P < 0.05). Working memory showed some improvement in both groups with no significant differences between the two groups. The authors conclude that over 1 year, there was a favorable effect of an energy-restricted, low-fat diet compared with an isocaloric low-carbohydrate diet on mood state and affect in overweight and obese individuals.


No firm conclusions should be drawn from this one small study about the affect of these two currently popular diet programs on mood. These interesting results do have some plausible physiologic explanation. Carbohydrates increase serotonin levels in the brain, and enhanced serotonin from dietary sources could improve mood states similar to the way in which most common anti-depressant medications enhance serotonin function.

Dietary modification for weight loss is a tricky business and whatever approach is chosen, it must be sustainable. We have learned that not all carbohydrates are created equal when it comes to their impact on hunger and overall calorie intake. Some carbohydrates, such as the simple sugars, have a high glycemic index, meaning that they cause blood sugar to rise quickly. This quick rise in blood sugar results in greater insulin secretion and a faster drop in blood sugar resulting in quicker hunger compared with more complex carbohydrates having a lower glycemic index. Eating carbohydrates with protein also results in an overall lower glycemic index and the Atkins diet promotes greater protein sources without attention to fat intake.

Eating a healthy diet and maintaining a healthy body weight are challenging goals for all of us and with the epidemic of overweight and obesity, a major part of clinical preventive medicine. Nutritional advice can be confusing and people vary in what they are willing to accept. Carbohydrates are important and it is likely they will always be the dominant food source. The key is to promote healthy carbohydrate sources from vegetables and fruits, both natural food sources. Whole grains are also important and care must be given to avoid overly refined and processed foods that become "junk calories." Healthy fats such as those in vegetable oils should be promoted in moderation while avoiding the unhealthy saturated and trans fats. I still find the 2-week food diary a great approach to getting started in helping patients analyze and improve their nutrition.

For those choosing an extreme diet of very low carbohydrates and no attention to fats, I will raise the question with them that this dietary approach may not be the best for their moods. Planting the seeds of feeling better may be an important adjunct to helping people eat better.