CBS News medical correspondent Dr. Jennifer Ashton explained new research about these diets and how they can affect your brain.
Ashton remarked that there's been a lot of controversy about which diet - low-carb or low-fat - is better for weight loss. However, according to a study in the Nov. 9 issue of Archives of Internal Medicine, suggests more than weight may be affected by your diet.
The study, conducted in Australia, Ashton said, took a look at a sampling of 106 obese or overweight people. Researchers followed them over a year. They found that those on the low carbohydrate diet were not in such a good mood at the end of that year.
But what contributed to this mood swing?
Ashton said people on low-carb diets can be very socially restricted and isolated.
She suggested people on low-carb diets "try to do anything with your friends or family" to keep you engaged with others.
The other theory, she said, is that carbohydrates can boost the chemical neurotransmitter in the brain called serotonin.
She explained, "[Seratonin] is one of the good mood hormones."
Ashton added that when you go on a diet, you can eat some carbohydrates, such as apples, berries and whole grains.
"Those are good sources that would be as effective for weight loss, but won't hurt you," she said.
But what if you're just trying to watch your weight - what should you watch out for if you have a carb craving?
Ashton said the "big offenders" in carbs are white breads and pastas and potatoes.
"They boost your insulin level, then you slam down and crash. You want to keep something that keeps your insulin levels a little more stable," she said. "Again, berries, fruits, whole grains, things like oatmeal, are much better for you."
Ashton added that the study both low-fat and low-carb diets are effective for weight loss. Both groups studied lost about 30 pounds on a 1,500 calorie diet over a year.
Still, Ashton said, "Those who restricted their carbohydrates weren't in such a good mood."
EXAMPLE OF LOW-FAT DIET:
LF 1433 kcal
300ml skim milk
2 slices wholegrain bread (40 g/slice)
40g high fibre cereal e.g. Fibre Plus, All Bran
20g reduced fat cheese (2 times/week)
150g (raw wt.) beef, chicken, pork, lamb (5 times/week)
150g fish (once/ week)
At least 2.5 cups vegetables
1 medium potato (3 times/ week)
100g (dry wt) pasta/rice (4 times/week)
100g bean/ lentils (2 times/week)
200g non-fat yogurt (3 times/week)
20g raw unsalted nuts
50g tinned fish (3 times/week)
2tsp polyunsaturated margarine
3 tsp vegetable oil e.g. olive or canola oil
EXAMPLE OF LOW-CARB DIET:
LC 1433 kcal
125ml full fat milk
70g full fat cheddar cheese
1 medium (50-55g) egg
300g (raw wt.) beef, chicken, fish
100g (cooked wt.) ham, tuna, beef, chicken, turkey
At least 2.5 cups (green) vegetables
25g (5tsp) oil/butter
40g raw, unsalted mixed nuts
2 standard alcoholic drinks/week (optional)