Beyond Energy Imbalance

A review of weight management research reveals how people lose weight—and keep it off.

Today, two out of three American adults are overweight or obese, and another 5.9% are now considered extremely obese (body mass index ≥ 40) (CDC). Excess weight increases the risk for heart disease, stroke, diabetes, several cancers, gallbladder disease and more. To fight the extra weight, Americans spend billions of dollars a year on diets and products promising weight loss, only to fail along the way. Considering these facts, it’s not surprising that clients approach you with questions about how to shed pounds fast.

You may offer guidance—within your scope of practice—about evidence-based dietary strategies that work for both weight loss and long-term maintenance. This information is important in the fight against obesity.

We know that overweight and obesity result from an energy imbalance, but the cause is multifactorial. Body weight is the result of genes, metabolism, behavior, environment, culture and socioeconomic status. A lucky few are genetically protected from gaining too much weight, while others seem destined to become overweight no matter what they do. The majority of people, however, fall somewhere in between. With a focus on individual dietary behavior, this article examines the most recent evidence available to help people successfully lose weight and keep it off.

Weight Loss Benefits

Lifestyle changes aimed at weight loss have numerous health benefits. A modest weight loss of 5%–10% of body weight can improve chronic-disease risk factors such as dyslipidemia (by raising HDL cholesterol levels and lowering levels of LDL cholesterol and triglycerides) and hypertension, and can also help control diabetes (Turk et al. 2009). A modest weight loss has been shown to reduce the rate of developing type 2 diabetes in individuals at risk for the disease (DPPRG 2009). Weight loss can also enhance athletic performance in events—such as distance running—where optimal body weight or a leaner, lighter physique is advantageous to competition.

While some studies suggest that calorie restriction and intentional weight loss benefit longevity, the evidence remains inconclusive. A recent review and meta-analysis of the effects of weight loss on mortality risk concluded that intentional weight loss had a small benefit for obese individuals with associated risk factors and no longevity benefit for healthy individuals, including the healthy obese (Harrington, Gibson & Cottrell 2009). The “healthy obese” are those who can be categorized as obese yet do not have any associated risk factors, such as high blood pressure, high cholesterol or diabetes.

Yes, excess weight can be a marker for factors that increase risk of disease and earlier death, but it remains questionable whether weight reduction alone should be a goal for individuals who are fit, eat well and are in overall good health despite being overweight. The long-term health effects of frequent dieting and weight cycling may actually be more harmful than maintaining one’s weight, even if it is higher than ideal. Among overweight and obese women, a more health-centered—rather than weight-centered—approach was shown to have beneficial effects on behavioral changes related to better weight maintenance. The benefits included restraint over food intake (Provencher et al. 2009).

Physiological & Psychological Factors in Weight Loss

“The major physiological influence on losing weight is to eat fewer calories than are necessary to maintain the weight you currently have, so that body fat stores are mobilized to make up the difference,” explains Carole Conn, PhD, RD, with the Nutrition and Dietetics Program at the University of New Mexico. “Energy in < energy out = weight loss” is a simple equation, but energy balance is a complex process. Everyone has a genetically determined set point—a weight range that the system strives to maintain. A person’s set point is influenced by behaviors and environment and, with persistent effort, it can be lowered.

The metabolic changes that occur with weight loss contribute to the challenges many people have with maintaining a lower weight. In most cases, metabolic rate slows, reducing total energy expenditure and resulting in fewer calories being needed to sustain energy needs. (However, if muscle mass can be retained, it is possible to sustain a higher metabolic rate with weight loss.) To meet basic needs, the brain then receives signals from the body—low blood sugar or shifting levels of various hormones that stimulate eating and tell us when we’ve had enough. “As weight is lost, physiological hunger may rise to replenish lost stores,” adds Conn. Additionally, environmental and emotional cues and the rewards of eating—including taste, texture and pleasure—can override normal signals of hunger and satiety and lead to overeating.

It takes a lot of commitment and mental and physical energy to lose weight and maintain the loss. Being ready to make changes is the first step, and this can be difficult when faced with major life stresses. Many people turn to food to deal with emotions, a pattern that can sabotage weight loss efforts. In short, losing and maintaining weight is more complicated than simply showing willpower.

Weight Control Strategies

Approximately one-third of weight lost on a diet is regained in the first year (Weiss et al. 2007). A thorough review of weight loss studies revealed that while people can lose 5%–10% of their weight in the first few months of a diet, within 4 or 5 years up to two-thirds of people regain even more weight than they lost (Mann et al. 2007).

To determine how others are successful, let’s turn to the National Weight Control Registry (NWCR) for clues. The NWCR tracks successful weight losers—individuals who have lost at least 30 pounds and kept it off for more than 1 year. The common behaviors these individuals share include monitoring weight and food intake, maintaining a low-calorie and low-fat diet, eating breakfast almost every day, engaging in 1 hour of physical activity daily and limiting television time to 10 hours or fewer per week (NWCR). A review of interventions supports these as beneficial strategies for weight loss and maintenance (Turk et al. 2009).

Following is an exploration of tried-and-true weight management methods.

Self-Monitoring

People who weigh themselves regularly are more successful at losing and maintaining their weight, as the monitoring process allows them to make adjustments if the weight creeps back (Butryn et al. 2007). Since many people grossly underestimate the number of calories they consume, a record of food intake can be a management tool. Becoming more mindful of what we eat, when, why and how is important for changing and maintaining behaviors.

Weight Control Tip. For consistency, choose a day and time to weigh yourself weekly, and tune in to how your clothes fit each day. For people who are just starting out, it’s wise to record daily dietary intake in order to learn about eating habits, triggers and where adjustments can be made. As weight is lost and new behaviors become habits, this may not be as necessary. Use a reliable online food record or a simple spiral notebook.

Eating Frequency & Pattern

When and how often one eats may determine weight. Studies show that eating four or five small meals/snacks throughout the day is associated with lower energy intake and reduced or no obesity risk, and eating less or more than this may actually increase the risk for obesity (Forslund et al. 2005; Ma et al. 2003), perhaps more so in men than women (Westerterp-Plantenga, Kovacs & Melanson 2003; Drummond et al. 1998).

Skipping breakfast is associated with a higher body mass index and increased obesity risk (Ma et al. 2003; Cho et al. 2003). So heed mom’s advice about eating breakfast; it will set you up for healthy eating the rest of the day. Because breakfast eaters maintain morning blood sugar levels, they are more likely to have better control over snack choices and eat less at later meals. Successful weight losers appreciate this and regularly eat a breakfast that contributes approximately 20% of their daily energy intake (Wyatt et al. 2002). While it’s true that the total calories consumed in a day matters more than when they’re eaten, to further support the benefits of a morning meal there is evidence that eating more calories earlier in the day versus later may help people manage weight (de Castro 2004; Forslund et al. 2002).

Weight Control Tip. Spread calories throughout the day. If you don’t eat breakfast, start eating a single item like a carton of low-fat yogurt or a banana within 1 hour of waking and then aim for a daily high-fiber breakfast made up of two to three different food groups.

Portion Control

There is plenty of research showing that the larger the portion served, the more a person will eat. This suggests a great strategy for parents trying to get their kids to eat vegetables but is a harsh reminder for everyone else. Studies demonstrate that when subjects consume more calories from large portions at a meal, hunger and fullness ratings are not affected and the subjects don’t compensate for the increased energy by eating less at subsequent meals (Wansink, Painter & North 2005; Rolls, Morris & Roe 2002). Bottom line: paying attention to portion size is a proven strategy that can help people reduce energy intake and lose weight. Eating slowly and savoring the food help control appetite and calorie intake. Shoveling food rapidly into the mouth blocks the body’s natural appetite control process. Kokkinoes et al. (2009) found higher levels of hormones that send a “fullness” signal to the brain in men who ate in a leisurely manner compared with those who devoured their food in minutes.

Weight Control Tip. Retrain skewed perceptions of what a serving is by measuring food for a few days with help from your hand: 1 cup = size of medium fist; serving of meat = medium-sized palm; cheese serving = two fingers; and a serving of oil = thumb tip. Teach yourself to slow down by choosing one meal a day (or week) that you purposely enjoy slowly, while sitting at a table.

Fill Up on Less

Increasing intake of nutrient-rich foods like fruits and vegetables is a positive strategy for controlling portions. Studies show that reducing energy density by boosting intake of low-caloric- density foods is associated with weight loss and improved diet quality (Ello-Martin et al. 2007; Ledikwe et al. 2007). Thanks to water and fiber, low-caloric-density foods offer larger portions with fewer calories, so you fill up without filling out. Examples include fruits, vegetables, beans and soups. High-fiber foods also slow digestion and absorption and stabilize blood sugar, which helps control hunger and further aids weight loss.

Adding foods rather than eliminating them helps people lose and maintain weight while feeling satisfied, both physically and emotionally. Following this approach, study participants report consuming more food by weight, while reducing energy intake (Ledikwe et al. 2007). They also report feeling less hungry (Ello-Martin et al. 2007). In the PREMIER study, the strongest predictor of weight loss was the decrease in food energy density, followed by changes in fiber intake (Ledikwe et al. 2007). Unfortunately, dietary fiber intake continues to be less than optimal.

Weight Control Tip. Fill up on nutrient-rich, high-fiber foods to satisfy hunger and reduce caloric intake. Adults should aim for 25–35 grams of fiber per day and increase gradually. To control calories, choose fresh, frozen or canned fruits without added sugar over fruit juice and dried fruits.

Source of Calories

Low-fat, high-protein, low-carb? Fad diets promising quick weight loss have confused people about what to eat. More than any food group or nutrient, carbohydrates have been vilified and blamed for America’s weight problem. Now here’s the evidence: it’s not the carbs that make you fat, but how much you eat. Regardless of source, calories eaten are converted to energy or stored in the body, and unless we use them (through physical activity and/or a reduction in calories so we draw on reserves), calories will settle as fat.

Cutting carbohydrates will reduce calories, but this is a short-term solution. Compared with other diets, a low-carbohydrate diet has been shown to result in lower body weight and greater fat loss in the first 6 months (Brehm et al. 2005; Samaha et al. 2003). However, at the 1- and 2-year marks, caloric intake and weight loss are similar across all participants, regardless of macronutrient composition (Sacks et al. 2009; Dansinger et al. 2005; Foster et al. 2003). Additionally, the safety of low-carb diets has not been evaluated long-term, and clients with certain health conditions should use them with caution.

Studies have dispelled the myth that any particular distribution of macronutrients confers overall advantages in terms of weight loss and maintenance (Sacks et al. 2009; Dale et al. 2009). That said, it’s important to keep in mind that some individuals can better maintain a reduced-calorie diet by cutting carbohydrates, while others find success with a lower-fat plan.

Weight Control Tip. Quality and quantity matter. Balance blood sugar and insulin levels by eating a combination of macronutrients at meals, focusing on fiber-rich carbohydrates (beans, vegetables, fruits and whole grains), lean protein and healthy fats to keep you full longer.

Low-Calorie Sweeteners

Information suggesting that low-calorie sweeteners increase appetite and cause people to gain weight continues to circulate. Yes, it’s calories that count, and incorporating foods and beverages with these sweeteners is one strategy employed by weight maintainers. But do low-calorie sweeteners increase appetite? “According to the American Dietetic Association’s position on sweeteners, replacing sugary foods with sugar substitutes can help consumers cut down on calories and control weight,” says Jenna A. Bell, PhD, RD, CSSD, co-author of Energy to Burn (Wiley 2009) and blogger for ChicagoNow.com/Eatright. “And the ADA agrees with other health organizations that there is good evidence that sugar substitutes, like aspartame, have no affect on appetite or food intake.” Recent reviews of studies support artificial sweeteners’ role in weight management (Mattes & Popkin 2009; Drewnowski & Bellisle 2007). The debate continues, and more research is needed.

Liquid Calories

Studies maintain that weight loss is positively associated with a reduction in sweetened-beverage consumption (Chen et al. 2009). However, the argument that all liquid calories promote weight gain because they are less satiating than solids, and that our body does not detect and therefore compensate for intake of liquid calories, is inconclusive (Drewnowski & Bellisle 2007). It also goes against clinical evidence, pointing to the effectiveness of meal replacement beverages for weight loss in overweight people who have difficulty self-selecting food choices. Liquid calories can lead to weight loss or weight gain—depending on how they’re used. “I see the issue of liquid calories as being one of volume,” adds Bell. “If you have to hold your to-go cup with two hands, it may have too many calories.”

Weight Control Tip. It’s wise to eat rather than drink the majority of your calories. Stick with water, unsweetened tea or coffee and beverages sweetened with low-calorie sweeteners to control calorie intake.

Small Changes Add Up

Many health experts contend that a “small changes” approach will work for weight loss and weight gain prevention. In a commentary published in the November 2009 issue of the Journal of the American Dietetic Association, researchers describe the “energy gap” as a tool that can be used to address the gradual weight gain that occurs from consuming slightly more energy than is expended each day. The energy gap is the degree of change that is needed in the energy balance point in order to reach desired body weight goals (e.g., to prevent weight gain or maintain weight loss). The researchers estimate that an energy gap of about 100 calories per day could theoretically prevent weight gain in most adults. Because energy needs are lower after weight loss, a larger energy gap is needed for maintenance, and this estimate is individualized. The authors provide an example: to maintain weight loss, an energy gap of about 200 calories per day is needed for a 220-pound person losing 10% of body weight. Since many people can lose weight, but very few are successful at maintaining the weight loss, promoting small, sustainable behavior changes may be one effective approach. Researchers contend that this may be a means to larger dietary and physical activity changes that can result in more significant weight loss (Hill, Peters & Wyatt 2009).

Weight control strategies should focus on reducing energy intake and increasing expenditure. Current physical activity recommendations of 60–90 minutes a day for maintaining weight loss may be difficult for some individuals to achieve or sustain. As clients strive to achieve this goal, applying individualized dietary strategies that work for successful weight losers—two examples are increasing fiber intake and including low-caloric-density foods—is crucial in helping individuals achieve and maintain a healthy weight.

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March 2010

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