Q I’ve lost 37 pounds on a low-carb diet, but I’m feeling so down. What can help?

A Women often struggle with moodiness on low-carb plans because the diet deprives the brain of its main source of fuel: glucose. Without this sugar, neurons can’t keep up the production of feel-good brain chemicals. In fact, in one study, subjects’ scores on depression tests doubled after 12 weeks on a low-carb diet.

Fortunately, it’s possible to slim without low moods. The key is to supplement with 1,000 mg of glutamine (like Life Extension L-glutamine, $10 for 50 servings, lef.com/ffw) twice daily between meals. The body converts this amino acid into a healthy source of glucose that fuels brain cells’ output of mood-boosting neurotransmitters. What’s more, glutamine stabilizes blood sugar and increases the production of appetite-suppressing hormones. As a result, women who take glutamine report feeling more energized and less hungry overall.