Peter H. Jones, MD, FACP, FNLA
The Skinny on Weight Loss
Every day in clinical practice we face the reality that many of our patients at risk for cardiovascular disease are obese. We also recognize that the usual measure of obesity—body mass index >30 kg/m2—strongly and linearly correlates with the prevalence of hypertension, type 2 diabetes mellitus (T2DM), and all-cause mortality, for both men and women. Another important comorbidity, obstructive sleep apnea, increases blood pressure and the incidence of atrial fibrillation and pulmonary hypertension, as well as sudden death. Therefore, weight loss could have an important impact on both short-term and long-term outcomes.
Is a Calorie a Calorie, No Matter the Source?
Although there are recent data indicating that weight loss resulting from bariatric surgery has been proved to reduce the prevalence of hypertension,1 sleep apnea, and T2DM, the data have been less impressive with respect to nonsurgical weight-loss techniques, principally because adherence/compliance to calorie-restriction diets is difficult. Nonetheless, there is evidence that a caloric-restriction lifestyle change can produce a modest weight loss (5% to 10% loss of baseline weight) that will not only prevent the progression of metabolic syndrome to T2DM (as shown in the Diabetes Prevention Program),2,3 but also improve glucose control in T2DM (the Look AHEAD trial).4,5
Clinicians and dietitians who recommend caloric-restricted diets struggle with many choices of how to compose such a plan. Does it matter whether the total calories are distributed as 20%/20%/60% protein/fat/carbohydrate versus 40%/20%/40% or 20%/40%/40% of protein/fat/carbohydrate,
respectively? In other words, is a calorie “in” the same regardless of its source?
The Role of Macronutrient Composition
Let’s examine the outcomes of several trials of different macronutrient composition with similar caloric content on the amount of weight loss and on cardiovascular risk markers. Foster and colleagues evaluated a low-carbohydrate diet (20g/d initially, increased to 40 g/d) versus a low-fat diet (<30%of calories) over 24 months.6 There was no difference in totalweight loss the first year (11% of baseline weight) and through the second year (7% of baseline weight) between the 2 diets. The low-carbohydrate diet produced greater reductions in triglycerides and diastolic blood pressure, and increases in high-density lipoprotein cholesterol (HDL-C),
but had less effect on low-density lipoprotein cholesterol (LDL-C) than the low-fat diet did.
Another study evaluated weight loss with an Atkins plan (low carbohydrate), Zone plan (equal percentages protein/ fat/carb), the LEARN diet, and the Ornish plan (low fat) over 12 months.7 The Atkins plan patients lost more weight than patients on the other diets (4.7 kg versus 2.2 kg) and they had greater increases in HDL-C and decreases in systolic blood pressure. In another study evaluating low- or highfat versus low- or high-protein diet combinations, there were similar weight reductions across the 4 dietary combinations over 24 months. LDL-C was reduced the most in the lowfat groups, while HDL-C increased and insulin decreased the most with the higher-protein groups (especially with the lower-carbohydrate diet).8 Finally, a study evaluation of the Atkins, Zone, Weight Watchers, and Ornish diets for 12
months demonstrated equal weight loss for all groups and no significant differences in risk markers.9 The key points to derive from these trials are that:
1. macronutrient composition does not matter when it comes to weight loss if the calorie-deficit plan is the same;
2. lower-carbohydrate diets produce greater reductions in blood pressure, glucose, and triglycerides, and increases in HDL-C, than do higher-carbohydrate diets; and
3. low-fat diets reduce LDL-C the most.
The Mediterranean Diet
One final comment about diet composition concerns the Mediterranean diet plan, which is high in monosaturated fat; includes daily intake of vegetables, meats, fruit, and whole grains; has protein sources primarily from fish and poultry; and limits red meat. Not only is this plan better for improving cardiovascular risk factors than a low-fat diet, it also reduces the risk of developing metabolic syndrome.10,11 As a long-term maintenance diet plan, the Mediterranean-style diet may be the most preferred.
The most challenging aspect of effective weight control is not the weight-loss component but rather the weight-maintenance part. While the concept of energy imbalance (calories “in” > calories “out”) is easy to understand as a cause of weight gain, the opposite is not so easy to determine for long-term weight control after a weight-loss intervention.The dynamic physiologic adaptations to weight loss lead to a downward change in both the resting energy expenditure (REE) and the energy cost of physical activity.12 Although less energy is stored in lean tissue (muscle) compared with fat, the lean tissue is more energetically expensive to maintain and therefore contributes the most to REE. Baseline REE has significant interindividual variation, but in general, men have higher lean tissue mass than women and with a similar macronutrient calorie-restricted diet will lose more body fat than women in a given time. After weight loss, being able to maintain lean tissue mass will minimize the tendency for REE to decline from its original baseline. Increasing physical activity can help somewhat with preserving REE; yet, one has to recognize that the energy expended to mobilize a more obese person is greater than for a less obese person after weight loss. As a result, for many people, increasing frequency and intensity of exercise after weight loss may only, at best, return them to the same REE level they had prior to loss. Therefore, a lower-than-expected daily caloric intake plus regular exercise may be needed just
to maintain weight loss. This aspect may be a challenge for patients to accept and to comply with, which is why regaining weight is so common.
A good review of all recent data about lifestyle modification, including exercise, for treating obesity was recently published.13 An interesting study of overfeeding people with a similar caloric amount from low-protein-containing foods versus high-protein-containing foods may help clinicians and patients understand that diet composition after weight loss may be important. This trial showed, as expected, similar weight gain for both groups, except for an increase in lean tissue and REE in the high-protein group compared with the low-protein group.14 In other words, the low-protein group stored more of the excess energy as fat, suggesting that the better maintenance diet would be one with higher protein as a percentage of daily calories, because it preserves lean tissue and REE even if there is a small increase in weight.
The Bottom Line
Thus, the bottom line for discussing weight-loss plans with
patients is as follows:
• Successful weight loss by nonsurgical methods involves significant calorie restriction (>500 cal/d), without concern about macronutrient composition.
• The choice of diet composition can be tailored to patient food choices, with the exception of favoring a lowcarbohydrate diet for patients with metabolic syndrome or diabetes.
• The initial goal is to lose 10% of baseline weight.
• Successful weight loss maintenance is more challenging, and must include the techniques of successful people documented in the National Weight Control Registry: selfmonitoring, eating breakfast, regular physical activity, and less TV watching.
• A maintenance diet should lean toward higher percentage of total calories as protein and a Mediterranean influence.
1. Schauer PR, Kashyap SR, Wolski K, et al. Bariatric surgery versus intensive medical therapy in obese patients with diabetes. N Eng J Med. doi:10.1056/NEJMoa1200225. Published April 26, 2012.
2. Knowler WC, Barrett-Conner E, Fowler SE, et al for the Diabetes Prevention Program Research Group. Reduction in the incidence of type 2 diabetes with lifestyle intervention on metformin. N Eng J Med. 2002;346:393-403.
3. Perreault L, MaY, Dagogo-Jack S, et al for the Diabetes Prevention Program. Sex differences in diabetes risk and the benefit of intensive lifestyle modification in the Diabetes Prevention Program. Diabetes Care. 2008;31:1416-1421.
4. Look AHEAD Research Group Pi-Sunyer X, Blackburn G Brancati FL, et al. Reduction in weight and cardiovascular disease risk factors in individuals with type 2 diabetes; one-year results of the Look AHEAD trial. Diabetes Care. 2007;30:1374-1383.
5. Look AHEAD Research Group. Long term effects of a lifestyle intervention on weight and cardiovascular risk factors in individuals with type 2 diabetes: four-year results of Look AHEAD Trial. Arch Intern Med. 2010;170:1566-1575.
6. Foster GD, Wyatt HR, Hill JO, et al. Weight and metabolic outcomes after 2 years on a low-carbohydrate versus low-fat diet. Ann Intern Med. 2010;153:147-157.
7. Gardner CD, Kiazand A, Alhassan S, et al. Comparison of the Atkins, Zone, Ornish and LEARN diets for change in weight and related risk factors among overweight premenopausal women: the A to Z Weight Loss Study. JAMA. 2007;297:969-977.
8. Sacks FM, Bray GA, Carey VJ, et al. Comparison of weight-loss diets with different compositions of fat, protein and carbohydrates. N Eng J Med. 2009;360:859-873.
9. Dansinger ML, Gleason JA, Griffin JL, et al. Comparison of the Atkins, Ornish, Weight Watchers and Zone diets for weight loss and heart disease risk reduction: a randomized trial. JAMA. 2005;293:43-53.
10. Kastorini CM, Millionis HJ, Esposito K, et al. The effect of Mediterranean diet on metabolic syndrome and its components. J Am Coll Cardiol. 2011;57:1299-1313.
11. Nordmann AJ, Suter-Zimmerman K, Bucher HC, et al. Metaanalysis comparing Mediterranean to low-fat diets for modification of cardiovascular risk factors. Am J Med. 2011;124:841-851.
12. Hall KD, Sacks G, Chandramohan D, et al. Quantification of the effect of energy imbalance on body weight. Lancet. 2011;278:826-837.
13. Wadden TA, Webb VL, Moran CH, Bailer BA. Lifestyle modification for obesity. Circulation. 2012;125:1157-1170.
14. Bray GA, Smith SR, deJonge L, et al. Effect of dietary protein content on weight gain, energy expediture and body composition during overeating: a randomized controlled trial. JAMA. 2012;307:47-55.