The investigators evaluate if changing eating habits and introducing a correct lifestyle in women with BMI >25 Kg/m2 would improve unfavorable maternal-fetal outcomes associated with excessive weight gain (EWG) during pregnancy. To pursue these goals, eligible women are randomly assigned to no intervention (Control group) that receive only a simple nutritional booklet about lifestyle and healthy diet during pregnancy without explicit caloric restriction or the Therapeutic Lifestyle Changes Program (TLC group) that receive a caloric restriction (1500 Kcal/day divided in3 main meals and 3 snacks + 300 kcal/die for overweight or 200 kcal/die for obese women submitted to energy expenditure program) associated to a mild physical activity (30 minutes at least 3 days/week) The investigators use a tool that could easily and practically evaluate not only total GWG at term, but also changes in maternal body composition: the bioimpedance analyzer.

Pregnant women, recruited from antenatal clinics, with pre-pregnancy BMI ≥ 25 kg/m2, age >18 years and single pregnancy are enrolled within 12th week at the Obstetric Unit of Policlinico Hospital of Modena.

Exclusion criteria are as follows: twin pregnancies, chronic diseases (i.e., diabetes mellitus, chronic hypertension, untreated thyroid diseases), gestational diabetes mellitus (GDM) in previous pregnancies, smoking during pregnancy, dietary supplements or herbal products known to affect body weight, other medical conditions that might affect body weight, and plans to deliver outside of the Birth Center.

At the first visit, an accurate obstetric history, family history, and personal history is collected for the assessment of exclusion criteria. The blood pressure, height and weight are measured, and the BMI is calculated.

Eligible women are randomly assigned to no intervention (Control group) or the Therapeutic Lifestyle Changes Program (TLC group). Randomization is performed using sealed envelopes(using a computer-generated random allocation). Study randomization is numbered and sealed in white envelops. Randomization occurs in consecutive order at time of the first visit. Due to study design, both gynecologist and dietitian know the allocation of the patient.

Every subject receives care in another institution (Antenatal Clinics of Modena Health program). Hence, women in both groups receive the same antenatal evaluation including two ultrasound examinations and at least 4 obstetric evaluations until term. However, referral gynecologists possibly know the allocated arm of their women.

Randomized subjects receive a 75-g 2-h Oral Glucose Tolerance Test (OGTT) at 16-18 and/or 24-28 weeks. The diagnosis of GDM is made for any glucose value exceeding the normal cut-off, as reported by the HAPO study. If OGTT is pathological, women are referred to other health care specialists.

Women randomized to both group are scheduled to have a specific follow-up for adherence to the program at 16, 20, 28, 36 weeks and 3 months after delivery also evaluating the fat mass, fat-free mass and total body water through the use of the bioimpedance analyzer. At baseline and 36 weeks each subject have to complete a Food Frequency Questionnaire (FFQ) to identify any change in eating habits. The FFQ includes questions about specific food items, such as the frequency of sauce consumption, the fat content of several food items, and seasonal consumption of fruit and vegetables. While the Control group receives only a simple nutritional booklet about a lifestyle (in accordance with Italian Guidelines for a healthy diet during pregnancy), the TLC Program includes a specific caloric restriction associated to a mild physical activity program.

The TLC diet comprises 1500 kcal/day and consists of 3 main meals and 3 snacks (breakfast, snack, lunch, snack, dinner, and evening snack) that corresponds to the baseline metabolism of a pregnant woman. The dietitian adds an amount of 200 kcal/day for obese or 300 kcal/day for overweight pregnant women submitted to physical activity program.The TLC diet has a target macronutrient composition of 55% carbohydrate, 20% protein, and 25% fat with moderately low saturated fat levels. The exercise intervention is focused on increasing walking and developing a more active lifestyle (i.e., walking rather than driving for short distances). The recommended exercise prescription for pregnant women is generally consistent with recommendations for the general adult population. However, it is important to monitor and adjust exercise prescriptions according to the woman's symptoms, discomforts, and abilities during pregnancy and be aware of contraindications for exercising during pregnancy. All participants are advised to participate in 30 min of moderate intensity activity at least 3 days a week. Subjects wear a pedometer (Omron Walking Style III HJ-203-EK) on a belt at the back of their waist during walking session for the assessment of the adherence to the physical activity program.

Inclusion Criteria:

• BMI ≥ 25 kg/m2
• age >18 years
• single pregnancy
• 1st trimester

Exclusion Criteria:

• twin pregnancies
• chronic diseases (i.e., diabetes mellitus, chronic hypertension, untreated thyroid diseases)
• Gestational diabetes mellitus in previous pregnancies
• smoking during pregnancy
• dietary supplements or herbal products known to affect body weight
• other medical conditions that might affect body weight
• to plan to deliver outside of the Birth Center.