AJCN 79:893S (May, 2004)"The Weight Debate: Balancing Food Consumption and Physical Activity"

"Recognizing that almost no family is spared and that even the very young are afflicted, the US government has finally declared war on obesity... Everyone seems to have the answer to lifelong weight control, but the answers are all different, and no validated, science-based, long-term solutions are in sight."

"Although the popular views hold taht our excess weight has accumulated because of massive food portions or couch potato behaviors, the average American adult gains <1kg/y. Only small, consistent increments in energy balance, <100 Calories/d, are needed to incite weight gains of this magnitude."

One article reviews factors other than food that affect metabolism and storage of fat. Another shows that small modifications in diet or exercise may have a large public health impact. One review suggests that regular milk consumption may really help control weight (see below). Finally - "Although most investigators and federal agencies agree that Americans need to be more physically active, the required dose and type of recommended activity remain controversial."

Article 1 Highlights: Is a calorie a calorie?: Burchholz pg 899S

Thermodynamics dictate that a calorie is a calorie. More research on weight loss and feeling "full" are needed to explain the increased weight loss for high-protein, low-carbohydrate diets. One reason low-carbohydrate diets seem successful initially is that one loses the glycogen which is stored in muscles to provide energy. When glycogen is lost from the body, so is lots of water stored in the muscle. So two-thirds of the weight loss is just water. Three studies, however, did follow the low-carbohydrate diet more than 10 weeks, and they found the weight loss was as effective as the low calorie diet.

Article 2 Highlights: Calcium and dairy products: Zemel pg 907S

Dietary calcium plays an important role in energy and weight control. High-calcium diets reduce fat storage and weight gain; they increase fat loss and heat generation burning calories. Also, low calcium intake stimulates fat cells. Specifically, dairy products are more effective than calcium supplements because of other bioactive compounds. The article supports use of 3 or more daily servings of dairy products. [see poster on dairy industry influence on US policy]

Article 3 Highlights: Physical activity: How much is enough?: Blair pg 913S

Current public health recommendations for physical activity are for 30 min of moderate-intensity activity each day. People who get more exercise will probably benefit even more. Exercise should include aerobic, resistance training, and flexibility exercises. This combination helps lean body mass, strength and endurance, preservation of function, and quality of life.

Table 1

The Institute of Medicine Committee on Dietary Intakes released a report in 2002. It calls for 60 min activity/day and "tends to dismiss as inadequate the consensus public health recommendation of 30 min activity/day."

This article disputes that report, presenting four reasons why 30 min/day might be sufficient. It argues that preventing weight gain is very complicated, so more data is necessary to decide whether 60 minutes is necessary. Clearly people are different genetically and behaviorally, and some people readily gain weight, while others do not. The article concludes that if 30 minutes and controlling calories does not control weight, then more exercise is recommended. In addition to aerobic exercise, weight training and flexibility exercises should be done at least twice a week.

NUTRITION INVESTIGATOR COMMENTS:

1. 30 minutes of exercise with strength, aerobic, and weight bearing exercises are a basic minimum for everyone almost every day.

2. For those who need to control their weight, 60 minutes of vigorous exercise per day is a good goal.

3. For those who need to control their weight, try a week or two consuming at least 3 servings of dairy products per week - milk, cheese, yoghurt, perhaps even ice cream. Keep track of your weight every day and see if it helps you.

4. See the essays on low-carbohydrate, Atkin's-like diets. For initial weight loss, they are very effective. For the long term, risks increase, so exercise and calorie control become the safe choice.